AP_BLHeli: use the HAL accessor for the MSP_UID reply

The MSP_UID handler read the MCU serial number by dereferencing
UDID_START, which only exists on ChibiOS, and the motor-mask debug line
used a %08lx specifier on a uint32_t. uint32_t is unsigned long on
arm-none-eabi, so the format was correct there and wrong everywhere
else. Neither is portable to SITL, so AP_BLHeli could only build for
ChibiOS targets.

Use hal.util->get_system_id_unformatted() so the reply works on any
HAL - on ChibiOS it does the same memcpy from UDID_START that this
replaces - and cast the mask to match the format. The reply stays a
fixed 12 bytes, zero padded, matching AP_MSP_Telem_Backend.

Co-authored-by: Peter Barker <pb-gh@barker.dropbear.id.au>

libraries/AP_BLHeli/AP_BLHeli.cpp

@@ -25,10 +25,6 @@
 
 #if HAVE_AP_BLHELI_SUPPORT
 
-#if CONFIG_HAL_BOARD == HAL_BOARD_CHIBIOS
-#include <hal.h>
-#endif
-
 #include <AP_Math/crc.h>
 #include <AP_Vehicle/AP_Vehicle_Type.h>
 #if APM_BUILD_TYPE(APM_BUILD_Rover)
@@ -415,11 +411,15 @@ void AP_BLHeli::msp_process_command(void)
         blheli.connected[blheli.chan] = false;
         break;
 
-    case MSP_UID:
+    case MSP_UID: {
         // MCU identifier
         debug("MSP_UID");
-        msp_send_reply(msp.cmdMSP, (const uint8_t *)UDID_START, 12);
+        uint8_t uid[12] {};
+        uint8_t len = sizeof(uid);
+        hal.util->get_system_id_unformatted(uid, len);
+        msp_send_reply(msp.cmdMSP, uid, sizeof(uid));
         break;
+    }
 
         // a literal "4" is used for the PWMType here to allow Rover
         // to use the same number for the same protocol.  At time of
@@ -1504,7 +1504,7 @@ void AP_BLHeli::init(uint32_t mask, AP_HAL::RCOutput::output_mode otype)
         }
     }
     motor_mask = mask;
-    debug("ESC: %u motors mask=0x%08lx", num_motors, digital_mask);
+    debug("%u motors mask=0x%08lx", num_motors, (unsigned long)digital_mask);
 
     // check if we have a combination of reversible and normal
     mixed_type = (mask != (mask & channel_reversible_mask.get())) && (channel_reversible_mask.get() != 0);