[mips][FastISel] Implement srem/urem and sdiv/udiv instructions.

Summary: Implement the LLVM assembly urem/srem and sdiv/udiv instructions in MIPS FastISel.

Based on a patch by Reed Kotler.

Test Plan:
srem1.ll
div1.ll
test-suite at O0/O2 for mips32 r1/r2

Reviewers: dsanders, rkotler

Subscribers: llvm-commits, rfuhler

Differential Revision: http://reviews.llvm.org/D7028

llvm-svn: 238757