efi_loader: allocate correct memory type for EFI image

The category of memory allocated for an EFI image should depend on
its type (application, bootime service driver, runtime service driver).

Our helloworld.efi built on arm64 has an illegal image type. Treat it
like an EFI application.

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