AP_HAL_ChibiOS: fix incorrect definition of AP_PERIPH_MAG_ENABLED for Here4AP #45945

Job	Run time
build (stm32f7, chibios, 10)	3m 42s
build (stm32h7, chibios, 10)	3m 18s
build (fmuv2-plane, chibios, 10)	1m 54s
build (periph-build, chibios, 10)	3m 46s
build (iofirmware, chibios, 10)	1m 33s
build (CubeOrange-bootloader, chibios, 10)	57s
build (fmuv3-bootloader, chibios, 10)	50s
build (revo-bootloader, chibios, 10)	51s
build (stm32h7-debug, chibios, 10)	2m 18s
build (fmuv3, chibios, 10)	5m 58s
build (revo-mini, chibios, 10)	4m 19s
build (MatekF405-Wing, chibios, 10)	4m 51s
build (CubeOrange-ODID, chibios, 10)	2m 42s
build (CubeRedPrimary-bootloader, chibios, 10)	57s
build (configure-all, chibios, 10)	11m 14s
build (build-options-defaults-test, chibios, 10)	7m 23s
build (signing, chibios, 10)	2m 41s
build (CubeOrange-PPP, chibios, 10)	2m 12s
build (CubeRed-EKF2, chibios, 10)	2m 4s
build (SOHW, chibios, 10)	3m 19s
build (Pixhawk6X-PPPGW, chibios, 10)	1m 36s
build (new-check, chibios, 10)	4m 29s
	1h 12m 54s

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