aarch64: Disassociate ls64 from simd

The ls64-related move expanders and splits required TARGET_SIMD.
That isn't necessary, since the 64-byte values are stored entirely
in GPRs.  (The associated define_insn was already correct.)

I wondered about moving the patterns to aarch64.md, but it wasn't
clear-cut.

gcc/
	* config/aarch64/aarch64-simd.md (movv8di): Remove TARGET_SIMD
	condition.  Likewise for the related define_split.  Tweak formatting.

gcc/testsuite/
	* gcc.target/aarch64/acle/ls64_asm_2.c: New test.