CarbonixF405: fix ESC[15] bug

This fixes an issue where an errant ESC[15] would show up for 5 seconds
after boot that would contain NaN values. This is related to a bug that
was years ago in ArduPilot: ArduPilot/ardupilot#22308

Basically, different areas of the code had different values for
ESC_TELEM_MAX_ESCS based which other header files were included at that
time.

SW-187

libraries/AP_HAL_ChibiOS/hwdef/CarbonixF405/hwdef.dat

@@ -120,4 +120,6 @@ define HAL_PERIPH_ENABLE_RC_OUT
 # enable ESC control
 define HAL_SUPPORT_RCOUT_SERIAL 1
 
-define HAL_PERIPH_ARM_MONITORING_ENABLE 1
+define HAL_PERIPH_ARM_MONITORING_ENABLE 1
+
+define NUM_SERVO_CHANNELS 2