arm64: add Permission Overlay Extension Kconfig

arm64: add Permission Overlay Extension Kconfig

Now that support for POE and Protection Keys has been implemented, add a
config to allow users to actually enable it.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20240822151113.1479789-24-joey.gouly@arm.com
Signed-off-by: Will Deacon <will@kernel.org>