efi_loader: refactor efi_setup_loaded_image()

Create the handle of loaded images and the EFI_LOADED_IMAGE_PROTOCOL
inside efi_setup_loaded_image(). Do not use local variables.

Currently we expect the loaded image handle to point to the loaded image
protocol. Additionally we have appended private fields to the protocol.

With the patch the handle points to a loaded image object and the private
fields are added here. This matches how we handle the net and the gop
object.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>