loader: edd_device_path_v3 is too small
The EDD v31, see table 13, page 33, does define device path as double
qword, that is, 16 bytes, we have only qword.
Also remove edd_device_path_v4 and edd_params_v4 because those are not used,
and there is no size difference in v3 versus v4.
Testing done: build/install/boot