efi: Generalize handle_ramdisks() and rename to handle_cmdline_files().

efi: Generalize handle_ramdisks() and rename to handle_cmdline_files().

The handle_cmdline_files now takes the option to handle as a string,
and returns the loaded data through parameters, rather than taking
an x86 specific setup_header structure.  For ARM, this will be used
to load a device tree blob in addition to initrd images.

Signed-off-by: Roy Franz <roy.franz@linaro.org>
Acked-by: Mark Salter <msalter@redhat.com>
Reviewed-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
(cherry picked from commit 46f4582e7cbc5f30127183812d4da875782518f5)
Signed-off-by: Mark Brown <broonie@linaro.org>