aarch64: Handle overlapping registers in movv8di [PR113550]

aarch64: Handle overlapping registers in movv8di [PR113550]

The LS64 movv8di pattern didn't handle loads that overlapped with
the address register (unless the overlap happened to be in the
last subload).

gcc/
	PR target/113550
	* config/aarch64/aarch64-simd.md: In the movv8di splitter, check
	whether each split instruction is a load that clobbers the source
	address.  Emit that instruction last if so.

gcc/testsuite/
	PR target/113550
	* gcc.target/aarch64/pr113550.c: New test.