[mips] Rename MipsAsmParser functions to conform to the LLVM Coding Standards....

[mips] Rename MipsAsmParser functions to conform to the LLVM Coding Standards. No functional changes.

Summary: There are still some functions which should be renamed, but they are inherited from the generic MC classes.

Reviewers: dsanders

Reviewed By: dsanders

Differential Revision: http://reviews.llvm.org/D5068

llvm-svn: 217145