arm64/sysreg: Add definition for HAFGRTR_EL2

arm64/sysreg: Add definition for HAFGRTR_EL2

Add a definition of HAFGRTR_EL2 (fine grained trap control for the AMU) as
per DDI0601 2023-09.

This was extracted from Fuad Tabba's patch "KVM: arm64: Handle
HAFGRTR_EL2 trapping in nested virt".

Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://lore.kernel.org/r/20231206100503.564090-6-tabba@google.com
[Extract sysreg update and rewrite commit message -- broonie]
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20231209-b4-arm64-sysreg-additions-v1-2-45284e538474@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>