AP_NavEKF3: ensure EK3 does not read GPS when disabled #42674

Job	Run time
build (stm32f7, chibios, 10)	14m 37s
build (stm32h7, chibios, 10)	13m 43s
build (fmuv2-plane, chibios, 10)	7m 15s
build (periph-build, chibios, 10)	12m 24s
build (iofirmware, chibios, 10)	4m 3s
build (CubeOrange-bootloader, chibios, 10)	3m 20s
build (fmuv3-bootloader, chibios, 10)	3m 20s
build (revo-bootloader, chibios, 10)	3m 4s
build (stm32h7-debug, chibios, 10)	8m 23s
build (fmuv3, chibios, 10)	14m 43s
build (revo-mini, chibios, 10)	11m 50s
build (MatekF405-Wing, chibios, 10)	12m 18s
build (CubeOrange-ODID, chibios, 10)	9m 35s
build (CubeRedPrimary-bootloader, chibios, 10)	3m 4s
build (configure-all, chibios, 10)	12m 46s
build (build-options-defaults-test, chibios, 10)	23m 42s
build (signing, chibios, 10)	9m 53s
build (CubeOrange-PPP, chibios, 10)	8m 7s
build (CubeRed-EKF2, chibios, 10)	8m 12s
build (SOHW, chibios, 10)	13m 49s
build (Pixhawk6X-PPPGW, chibios, 10)	4m 21s
build (new-check, chibios, 10)	14m 17s
	3h 36m 46s

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