aarch64: Update cpuinfo strings for some arch features

aarch64: Update cpuinfo strings for some arch features

The entries for some recently-added arch features were missing the cpuinfo
string used in -march=native detection.  Presumably the Linux kernel had not
specified such a string at the time the GCC support was added.
But I see that current versions of Linux do have strings for these features
in the arch/arm64/kernel/cpuinfo.c file in the kernel tree.

This patch adds them.  This fixes the strings for the f32mm and f64mm features
which I think were using the wrong string.  The kernel exposes them with an
"sve" prefix.

Bootstrapped and tested on aarch64-none-linux-gnu.

Signed-off-by: Kyrylo Tkachov <ktkachov@nvidia.com>
gcc/

	* config/aarch64/aarch64-option-extensions.def (sve-b16b16,
	f32mm, f64mm, sve2p1, sme-f64f64, sme-i16i64, sme-b16b16,
	sme-f16f16, mops): Update FEATURE_STRING field.