Ignore the .interp section in the arm64 EFI loader

When building the loader an unneeded .interp section may be added. Move
this to the unused section region so offsets of used sections don't
change.

Obtained from: CheriBSD
Sponsored by: Innovate UK

(cherry picked from commit 6215ed7c5c0e8cdd536123ec658a081748cfc85c)