[Mips] Change std::sort to llvm::sort in response to r327219

[mgrang]

Summary

r327219 added wrappers to std::sort which randomly shuffle the container before sorting.
This will help in uncovering non-determinism caused due to undefined sorting
order of objects having the same key.

To make use of that infrastructure we need to invoke llvm::sort instead of std::sort.

Note: This patch is one of a series of patches to replace *all* std::sort to llvm::sort.
Refer the comments section in D44363 for a list of all the required patches.

[RKSimon]

SGTM but the other Simons @sdardis @atanasyan need to have the final yes/no, I guess non-Simons can have their say as well....

[atanasyan]

LGTM

lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm,
   // rather than it being split across a pair of relocations.
   if (hasRelocationAddend())
     return;
 
   if (Relocs.size() < 2)
     return;
 
   // Sort relocations by the address they are applied to.
-  std::sort(Relocs.begin(), Relocs.end(),
+  llvm::sort(Relocs.begin(), Relocs.end(),
              [](const ELFRelocationEntry &A, const ELFRelocationEntry &B) {
                return A.Offset < B.Offset;
              });
 
   std::list<MipsRelocationEntry> Sorted;
   std::list<ELFRelocationEntry> Remainder;
 
   DEBUG(dumpRelocs("R: ", Relocs));
 
   // Separate the movable relocations (AHL relocations using the high bits) from
   // the immobile relocations (everything else). This does not preserve high/low