Revert header changes

Revert "Do the same for ia32..."
and "Generate a sane PE header on shim, fallback, and MokManager."
This reverts commit 6744a7ef8eca44948565c3d1244ec931ed3f6fee.
and commit 0e7ba5947eb38b79de2051ecf3b95055e620475c.

These are premature and I can do this without such drastic measures.

Signed-off-by: Peter Jones <pjones@redhat.com>
Actually find the relocations correctly and process them that way.

Find the relocations based on the *file* address in the old binary,
because it's only the same as the virtual address some of the time.

Also perform some extra validation before processing it, and don't bail
out in /error/ if both ReloceBase and RelocEnd are null - that condition
is fine.

Signed-off-by: Peter Jones <pjones@redhat.com>