[ELF2] Sort dynamic symbols according to the MIPS requirements.

The MIPS ABI has requirements to sort the entries in the .dyn.sym section.
Symbols which are not in the GOT have to precede the symbols which are added to
the GOT. The latter must have the same order as the corresponding GOT entries.

Since these sorting requirements contradict those of the GNU hash section,
they cannot be used together.

Differential revision: http://reviews.llvm.org/D14281

llvm-svn: 252854