[FMV][AArch64] Remove last of MRS bits and rename file (#161585)

474f5d2aefb44430b89ed72774a3c1d26a0adfb1 removed the last
bits reading from system registers so remove the last bits
utilizing MRS and rename the file to hwcap as the
code is now only decoding the hwcap flags.

GitOrigin-RevId: ea443d528d1a6687c2f5ecfe3de62e5c9d2ca42c
2 files changed