[mips] Rename emit and parse functions for the .cpload assembler directive. NFC.

Summary: It's better if we have a consistent name for .cpload-related functions.

Reviewers: dsanders

Reviewed By: dsanders

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5437

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218768 91177308-0d34-0410-b5e6-96231b3b80d8