RISC-V: Remove RV128-only fmv instructions

RISC-V: Remove RV128-only fmv instructions

As fmv.x.q and fmv.q.x instructions are RV128-only (not RV64-only),
it should be removed until RV128 support for GNU Binutils is required
again.

gas/ChangeLog:

	* testsuite/gas/riscv/fmv.x.q-rv64-fail.d: New failure test.
	* testsuite/gas/riscv/fmv.x.q-rv64-fail.l: Likewise.
	* testsuite/gas/riscv/fmv.x.q-rv64-fail.s: Likewise.

include/ChangeLog:

	* opcode/riscv-opc.h (MATCH_FMV_X_Q, MASK_FMV_X_Q,
	MATCH_FMV_Q_X, MASK_FMV_Q_X): Remove RV128-only instructions.

opcodes/ChangeLog:

	* riscv-opc.c (riscv_opcodes): Remove RV128-only instructions.