arm64: Restrict undef hook for cpufeature registers

arm64: Restrict undef hook for cpufeature registers

This commit modifies the mask of the mrs_hook declared in
arch/arm64/kernel/cpufeatures.c which emulates only feature register
access. This is necessary because this hook's mask was too large and
thus masking any mrs instruction, even if not related to the emulated
registers which made the pmu emulation inefficient.

Signed-off-by: Raphael Gault <raphael.gault@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210517180256.2881891-1-robh@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>