arm64: sysreg: add register encodings used by KVM

arm64: sysreg: add register encodings used by KVM

This patch adds sysreg definitions for registers which KVM needs the
encodings for, which are not currently describe in <asm/sysregs.h>.
Subsequent patches will make use of these definitions.

The encodings were taken from ARM DDI 0487A.k_iss10775, Table C5-6, but
this is not an exhaustive addition. Additions are only made for
registers used today by KVM.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will.deacon@arm.com>