Restore protection flags for ifunc during relocs.

IFUNC relocations require executable flag for the load
segment containing .text. When dso has text relocs linker
removes exec which causes crash during ifunc relocations.

This patch fixes this problem by restoring segments protection
for ifunc relocs.

Bug: http://b/22611399
Change-Id: Icbf3be0fec0e42bf805bcad7533e2032a2e11b9c