AP_HAL_ChibiOS: add support for using smps to supply external power #176

Job	Run time
build (stm32f7, chibios, 10)	16m 37s
build (stm32h7, chibios, 10)	15m 16s
build (fmuv2-plane, chibios, 10)	8m 8s
build (periph-build, chibios, 10)	16m 42s
build (iofirmware, chibios, 10)	4m 36s
build (CubeOrange-bootloader, chibios, 10)	3m 19s
build (fmuv3-bootloader, chibios, 10)	3m 15s
build (revo-bootloader, chibios, 10)	3m 16s
build (stm32h7-debug, chibios, 10)	9m 15s
build (fmuv3, chibios, 10)	15m 54s
build (revo-mini, chibios, 10)	5m 32s
build (MatekF405-Wing, chibios, 10)	6m 3s
build (CubeOrange-ODID, chibios, 10)	10m 29s
build (CubeRedPrimary-bootloader, chibios, 10)	3m 34s
build (configure-all, chibios, 10)	12m 1s
build (build-options-defaults-test, chibios, 10)	28m 42s
build (signing, chibios, 10)	6m 56s
build (CubeOrange-PPP, chibios, 10)	9m 0s
build (SOHW, chibios, 10)	15m 7s
build (Pixhawk6X-PPPGW, chibios, 10)	2m 16s
	3h 15m 58s

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