KVM: arm64: Allow SMCCC_ARCH_WORKAROUND_3 to be discovered and migrated

commit a5905d6a upstream.

KVM allows the guest to discover whether the ARCH_WORKAROUND SMCCC are
implemented, and to preserve that state during migration through its
firmware register interface.

Add the necessary boiler plate for SMCCC_ARCH_WORKAROUND_3.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
[ kvm code moved to virt/kvm/arm. ]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>