Add support for the new names of the RISC-V fmv.x.s and fmv.s.x instructions,...

Add support for the new names of the RISC-V fmv.x.s and fmv.s.x instructions, vis: fmv.x.w and fmv.w.x.

	PR 22179
opcodes	* riscv-opc.c (riscv_opcodes): Add fmv.x.w and fmv.w.x as the new
	names for the fmv.x.s and fmv.s.x instructions respectively.

gas	* testsuite/gas/riscv/fmv.x.s: New file: Tests the support for the
	renamed fmv.x.s and fmv.s.x instructions.
	* testsuite/gas/riscv/fmv.x.d: New file: Test driver.