ChibiOS generator should reject overlapping definitions

[WickedShell]

Bug report

Issue details

It's possible to define multiple pins to the same define, which is silently accepted by the generator. This should be caught as a fatal build error when processing the hwdef.dat. For example the following will currently generate without any issues, even though there is a duplicate definition for AUX_ADC2:

--- a/libraries/AP_HAL_ChibiOS/hwdef/fmuv3/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/fmuv3/hwdef.dat
@@ -279,7 +279,7 @@ PC1 MAG_CS CS
 PC2 MPU_CS CS
 
 # This defines more ADC inputs.
-PC3 AUX_POWER ADC1 SCALE(1)
+PC3 AUX_ADC2 ADC1 SCALE(1)
 PC4 AUX_ADC2 ADC1 SCALE(1)
 
 # And the analog input for airspeed (rarely used these days).

Version
7fda309

Platform
[ x ] All
[ ] AntennaTracker
[ ] Copter
[ ] Plane
[ ] Rover
[ ] Submarine