arm64: entry: Allow handling of undefined instructions from EL1

[ Upstream commit 0bf0f444b2c49241b2b39aa3cf210d7c95ef6c34 ]

Rather than panic() when taking an undefined instruction exception from
EL1, allow a hook to be registered in case we want to emulate the
instruction, like we will for the SSBS PSTATE manipulation instructions.

Change-Id: I283fa8f4e8f4ebb078b4455342a6cd3501447157
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: 0bf0f444b2c49241b2b39aa3cf210d7c95ef6c34
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[groverm@codeaurora: Resolve merge conflicts]
Signed-off-by: Mayank Grover <groverm@codeaurora.org>