CxVersion: move include file to AP_FWVersion.h

[robertlong13]

Previously LoggerMessageWriter wasn't correctly seeing that we had defined a custom fw string, so it was only logging our custom string message to the log, and leaving out the ArduPlane X.Y.Z string.

Relevant part of the code:

carbopilot_V2/libraries/AP_Logger/LoggerMessageWriter.cpp

Lines 284 to 296 in f40d82e

	case Stage::FIRMWARE_STRING:
	#ifdef AP_CUSTOM_FIRMWARE_STRING
	// also log original firmware string if different
	if (! _logger_backend->Write_MessageF("%s [%s]",
	fwver.fw_string,
	fwver.fw_string_original)) {
	return; // call me again
	}
	#else
	if (! _logger_backend->Write_Message(fwver.fw_string)) {
	return; // call me again
	}
	#endif

Before:
CxPilot-7.0.0dev (F40D82EA)

After:
CxPilot-7.0.0dev (F40D82EA) [ArduPlane V4.5.6]"

Tested that plot.ardupilot.org now recognizes our logs as planes instead of quads.