Shadow stacks are not available in the EFI stub, filter out SCS flags.
Suggested-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NSami Tolvanen <samitolvanen@google.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Acked-by: NArd Biesheuvel <ardb@kernel.org>
Signed-off-by: NWill Deacon <will@kernel.org>