Copter: cleanup EKF failsafe units and division #35566

Job	Run time
build (stm32f7, chibios, 10)	4m 7s
build (stm32h7, chibios, 10)	3m 28s
build (fmuv2-plane, chibios, 10)	1m 49s
build (periph-build, chibios, 10)	5m 2s
build (iofirmware, chibios, 10)	1m 26s
build (CubeOrange-bootloader, chibios, 10)	1m 0s
build (fmuv3-bootloader, chibios, 10)	1m 10s
build (revo-bootloader, chibios, 10)	55s
build (stm32h7-debug, chibios, 10)	2m 15s
build (fmuv3, chibios, 10)	5m 24s
build (revo-mini, chibios, 10)	4m 4s
build (MatekF405-Wing, chibios, 10)	4m 16s
build (CubeOrange-ODID, chibios, 10)	2m 58s
build (CubeRedPrimary-bootloader, chibios, 10)	50s
build (configure-all, chibios, 10)	9m 18s
build (build-options-defaults-test, chibios, 10)	6m 1s
build (signing, chibios, 10)	3m 0s
build (CubeOrange-PPP, chibios, 10)	2m 25s
build (CubeOrange-SOHW, chibios, 10)	2m 1s
build (Pixhawk6X-PPPGW, chibios, 10)	1m 16s
	1h 2m 45s

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