aarch64: Remove VALL_F16MOV iterator

aarch64: Remove VALL_F16MOV iterator

The VALL_F16MOV iterator now has the same modes as VALL_F16,
in the same order.  This patch removes the former in favour
of the latter.

This doesn't fix a bug as such, but it's ultra-safe (no change in
object code) and it saves a follow-up patch from having to make
a false choice between the iterators.

gcc/
	* config/aarch64/iterators.md (VALL_F16MOV): Delete.
	* config/aarch64/aarch64-simd.md (mov<mode>): Use VALL_F16 instead
	of VALL_F16MOV.