[mips][ias] Prevent double-filling of delay slots by generating '.set noreorder' regions.

Summary:
When clang is given -save-temps or -via-file-asm, any inline assembly in
the source is parsed twice. Once by the compiler, and again by the
assembler. We must take care to ensure that this doesn't lead to
double-filling delay slots.

Reviewers: sdardis, vkalintiris

Subscribers: dsanders, sdardis, llvm-commits

Differential Revision: http://reviews.llvm.org/D19166

llvm-svn: 266608