hwdef: enable IMU in HolybroG4_GPS #41695

Job	Run time
build (base)	2m 11s
build (clang)	1m 59s
build-gcc-heli	2m 9s
autotest-heli (sitltest-heli)	10m 21s
autotest (sitltest-copter-tests1a)	7m 31s
autotest (sitltest-copter-tests1b)	9m 18s
autotest (sitltest-copter-tests1c)	11m 38s
autotest (sitltest-copter-tests1d)	8m 52s
autotest (sitltest-copter-tests1e)	9m 12s
autotest (sitltest-copter-tests2a)	8m 59s
autotest (sitltest-copter-tests2b)	29m 25s
	1h 41m 35s

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