mips-msa.md (msa_insert_<msaftm_f>): Add an alternative which covers the floating-point input value.

        * config/mips/mips-msa.md (msa_insert_<msaftm_f>): Add an
        alternative which covers the floating-point input value. Also
        forbid the split of insert.d pattern for floating-point values.

        * gcc.target/mips/msa-insert-split.c: New test.

From-SVN: r277533