linker: restore prelink support

Prelink support is required to load old vendor binary blobs
on many devices properly

This commit partially reverts 4688279db5dcc4004941e7f133c4a1c3617d842c

Picked from android-4.3. This solves Baseband issue on legacy devices.

Conflicts:
	linker/linker_phdr.cpp
	linker/linker_phdr.h

Change-Id: I09401e22c7fc87c4babdc1365ff5fd9bd8520c70
Signed-off-by: Humberto Borba <humberos@gmail.com>