arm: Add support for Armv8.9-A and Armv9.4-A

This patch adds AArch32 support for -march=armv8.9-a and
-march=armv9.4-a. The behaviour of the new options can be
expressed using a combination of existing feature flags
and tables.

The cpu_arch_ver entries for ARM_ARCH_V9_4A and ARM_ARCH_V8_9A
are technically redundant but it including them for macro code
consistency across architectures.