aarch64: testsuite: Fix do-assemble tests for SME

aarch64: testsuite: Fix do-assemble tests for SME

GCC doesn't support SME without SVE2, so the -march=armv8-a+<ext> argument to
check_no_compiler_messages causes aarch64_asm_<ext>_ok to return zero for SME
and any <ext> that implies it.

This patch changes the baseline architecure to armv9-a for these extensions.

gcc/testsuite/ChangeLog:

	* lib/target-supports.exp: Split the extensions that require SME into
	a separate set, and use armv9-a as their baseline.

(cherry picked from commit 9793ffce9332349441b5c83f8c1809ac4264a0f2)