efi: Print the secure boot status in x86 setup_arch()

Print the secure boot status in the x86 setup_arch() but otherwise do
nothing more for now. More functionality will be added later, but this at
least allows for testing.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
[ardb: use efi_enabled() instead of IS_ENABLED(CONFIG_EFI)]
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>