efi_loader: add firmware management protocol for raw image

In this commit, a very simple firmware management protocol driver
is implemented. It will take a binary image in a capsule file and
apply the data using dfu backend storage drivers via dfu_write_by_alt()
interface.

So "dfu_alt_info" variable should be properly set to specify a device
and location to be updated. Please read README.dfu.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>