arch-arm: Remove unusued MISCREG_A64_UNIMPL

In case the decoder fails to find a suitable MiscReg during a MSR/MRS
in AArch64, MISCREG_UNKNOWN is used, so there is no need for an extra
MISCREG_A64_UNIMPL register.

Change-Id: I7c709fc554e554b39d765dffb7ceb90e33b7c15f
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/10503
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
2 files changed