AP_NavEKF2: stop including AP_DAL.h in header #39506

Job	Run time
build (base)	8m 47s
build (clang)	10m 55s
build-gcc-heli	8m 53s
autotest-heli (sitltest-heli)	13m 40s
autotest (sitltest-copter-tests1a)	11m 45s
autotest (sitltest-copter-tests1b)	13m 55s
autotest (sitltest-copter-tests1c)	15m 43s
autotest (sitltest-copter-tests1d)	13m 25s
autotest (sitltest-copter-tests1e)	13m 24s
autotest (sitltest-copter-tests2a)	13m 25s
autotest (sitltest-copter-tests2b)	33m 41s
	2h 37m 33s

Provide feedback