AArch64: Do not allow SIMD clones with simdlen 1 [PR113552]

The AArch64 vector PCS does not allow simd calls with simdlen 1,
however due to a bug we currently do allow it for num == 0.

This causes us to emit a symbol that doesn't exist and we fail to link.

gcc/ChangeLog:

	PR tree-optimization/113552
	* config/aarch64/aarch64.cc
	(aarch64_simd_clone_compute_vecsize_and_simdlen): Block simdlen 1.

gcc/testsuite/ChangeLog:

	PR tree-optimization/113552
	* gcc.target/aarch64/pr113552.c: New test.
	* gcc.target/aarch64/simd_pcs_attribute-3.c: Remove bogus check.