RISC-V: Make g imply zmmul extension.

bfd/
	* elfxx-riscv.c (riscv_implicit_subset): Moved entry of m after g,
	so that g can imply zmmul.
gas/
	* testsuite/gas/riscv/attribute-01.d: Updated.
	* testsuite/gas/riscv/attribute-02.d: Likewise.
	* testsuite/gas/riscv/attribute-03.d: Likewise.
	* testsuite/gas/riscv/attribute-04.d: Likewise.
	* testsuite/gas/riscv/attribute-05.d: Likewise.
	* testsuite/gas/riscv/attribute-10.d: Likewise.
	* testsuite/gas/riscv/march-imply-g.d: Likewise.
	* testsuite/gas/riscv/march-imply-unsupported.d: Likewise.