[mips][msa] Implemented insert_vector_elt for v4f32 and v2f64.

For v4f32 and v2f64, INSERT_VECTOR_ELT is matched by a pseudo-insn which is
later expanded to appropriate insve.[wd] insns.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191515 91177308-0d34-0410-b5e6-96231b3b80d8