loader: implement MEDIA_FILEPATH_DP support in efipart

The efipart rework did break the ARM systems as the new code is
using more exact filters to sort the devices and we need to
add support for MEDIA_FILEPATH_DP device paths.

PR: 216940
Reported by: karl@denninger.net
Reviewed by: allanjude, manu
Approved by: allanjude (mentor)
Differential Revision: https://reviews.freebsd.org/D9520