efi/x86: Move efi=debug option parsing to core

fed6cefe

 ("x86/efi: Add a "debug" option to the efi= cmdline")
adds the DBG flag, but does so for x86 only. Move this early param
parsing to core code.

Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Mark Salter <msalter@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>