RISC-V: Add missing hint instructions from RV128I.
gas/
* testsuite/gas/riscv/c-zero-imm.d: Add more tests.
* testsuite/gas/riscv/c-zero-imm.s: Likewise.
* testsuite/gas/riscv/c-zero-reg.d: Fix typo in test. Add disabled
future test for RV128 support.
* testsuite/gas/riscv/c-zero-reg.s: Likewise.
include/
* opcode/riscv-opc.h (MATCH_C_SRLI64, MASK_C_SRLI64): New.
(MATCH_C_SRAI64, MASK_C_SRAI64): New.
(MATCH_C_SLLI64, MASK_C_SLLI64): New.
opcodes/
* riscv-opc.c (match_c_slli, match_slli_as_c_slli): New.
(match_c_slli64, match_srxi_as_c_srxi): New.
(riscv_opcodes) <slli, sll>: Use match_slli_as_c_slli.
<srli, srl, srai, sra>: Use match_srxi_as_c_srxi.
<c.slli, c.srli, c.srai>: Use match_s_slli.
<c.slli64, c.srli64, c.srai64>: New.
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