Heli Swashplate: Make motor numbers const #38358

Job	Run time
build (stm32f7, chibios, 10)	6m 4s
build (stm32h7, chibios, 10)	4m 58s
build (fmuv2-plane, chibios, 10)	2m 49s
build (periph-build, chibios, 10)	3m 42s
build (iofirmware, chibios, 10)	1m 28s
build (CubeOrange-bootloader, chibios, 10)	1m 9s
build (fmuv3-bootloader, chibios, 10)	49s
build (revo-bootloader, chibios, 10)	50s
build (stm32h7-debug, chibios, 10)	3m 29s
build (fmuv3, chibios, 10)	7m 58s
build (revo-mini, chibios, 10)	6m 12s
build (MatekF405-Wing, chibios, 10)	6m 49s
build (CubeOrange-ODID, chibios, 10)	4m 27s
build (CubeRedPrimary-bootloader, chibios, 10)	49s
build (configure-all, chibios, 10)	9m 5s
build (build-options-defaults-test, chibios, 10)	12m 16s
build (signing, chibios, 10)	3m 40s
build (CubeOrange-PPP, chibios, 10)	3m 15s
build (SOHW, chibios, 10)	5m 5s
build (Pixhawk6X-PPPGW, chibios, 10)	1m 16s
	1h 26m 10s

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