Removes units on messages with hdop, vdop (mavlink#1580)

This removes the units from the HDOP, VDOP (fields are generally named eph, epv) on messages because they are defined as unitless.

message_definitions/v1.0/common.xml

@@ -5278,8 +5278,8 @@
       <field type="int32_t" name="lat" units="degE7">Latitude (WGS84)</field>
       <field type="int32_t" name="lon" units="degE7">Longitude (WGS84)</field>
       <field type="int32_t" name="alt" units="mm">Altitude (MSL). Positive for up.</field>
-      <field type="uint16_t" name="eph" units="cm">GPS HDOP horizontal dilution of position. If unknown, set to: 65535</field>
-      <field type="uint16_t" name="epv" units="cm">GPS VDOP vertical dilution of position. If unknown, set to: 65535</field>
+      <field type="uint16_t" name="eph">GPS HDOP horizontal dilution of position (unitless). If unknown, set to: UINT16_MAX</field>
+      <field type="uint16_t" name="epv">GPS VDOP vertical dilution of position (unitless). If unknown, set to: UINT16_MAX</field>
       <field type="uint16_t" name="vel" units="cm/s">GPS ground speed. If unknown, set to: 65535</field>
       <field type="int16_t" name="vn" units="cm/s">GPS velocity in north direction in earth-fixed NED frame</field>
       <field type="int16_t" name="ve" units="cm/s">GPS velocity in east direction in earth-fixed NED frame</field>
@@ -5393,8 +5393,8 @@
       <field type="int32_t" name="lat" units="degE7">Latitude (WGS84)</field>
       <field type="int32_t" name="lon" units="degE7">Longitude (WGS84)</field>
       <field type="int32_t" name="alt" units="mm">Altitude (MSL). Positive for up.</field>
-      <field type="uint16_t" name="eph" units="cm">GPS HDOP horizontal dilution of position. If unknown, set to: UINT16_MAX</field>
-      <field type="uint16_t" name="epv" units="cm">GPS VDOP vertical dilution of position. If unknown, set to: UINT16_MAX</field>
+      <field type="uint16_t" name="eph">GPS HDOP horizontal dilution of position (unitless). If unknown, set to: UINT16_MAX</field>
+      <field type="uint16_t" name="epv">GPS VDOP vertical dilution of position (unitless). If unknown, set to: UINT16_MAX</field>
       <field type="uint16_t" name="vel" units="cm/s">GPS ground speed. If unknown, set to: UINT16_MAX</field>
       <field type="uint16_t" name="cog" units="cdeg">Course over ground (NOT heading, but direction of movement): 0.0..359.99 degrees. If unknown, set to: UINT16_MAX</field>
       <field type="uint8_t" name="satellites_visible">Number of satellites visible. If unknown, set to 255</field>
@@ -5764,8 +5764,8 @@
       <field type="int32_t" name="lat" units="degE7">Latitude (WGS84)</field>
       <field type="int32_t" name="lon" units="degE7">Longitude (WGS84)</field>
       <field type="float" name="alt" units="m">Altitude (MSL). Positive for up.</field>
-      <field type="float" name="hdop" units="m">GPS HDOP horizontal dilution of position</field>
-      <field type="float" name="vdop" units="m">GPS VDOP vertical dilution of position</field>
+      <field type="float" name="hdop">GPS HDOP horizontal dilution of position (unitless). If unknown, set to: UINT16_MAX</field>
+      <field type="float" name="vdop">GPS VDOP vertical dilution of position (unitless). If unknown, set to: UINT16_MAX</field>
       <field type="float" name="vn" units="m/s">GPS velocity in north direction in earth-fixed NED frame</field>
       <field type="float" name="ve" units="m/s">GPS velocity in east direction in earth-fixed NED frame</field>
       <field type="float" name="vd" units="m/s">GPS velocity in down direction in earth-fixed NED frame</field>