[mips] Add PTR_64 and GPR_64 predicates to some MIPS 64-bit instructions

Add `IsGP64bit` and `IsPTR64bit` to the list of `UnsupportedFeatures`
of the P5600 scheduling definitions. Also mark some MIPS 64-bit
instructions by PTR_64 and GPR_64 predicates. This reduces number
of "No schedule information for" and "lacks information for" errors
in case of marking this scheduler model as complete.

This patch is one of a series of patches. The goal is to make P5600
scheduler model complete and turn on the `CompleteModel` flag.

Differential Revision: https://reviews.llvm.org/D63237

llvm-svn: 363702