[MIPS GlobalISel] Select copy for arguments from FPRBRegBank

Move selectCopy into MipsInstructionSelector class.
Select copy for arguments from FPRBRegBank for MIPS32.

Differential Revision: https://reviews.llvm.org/D59644


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356886 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed