RISC-V: Fix 4-arg add parsing.

RISC-V: Fix 4-arg add parsing.

	PR gas/23956
	gas/
	* config/tc-riscv.c (validate_riscv_insn) <'1'>: New case.
	(percent_op_null): New.
	(riscv_ip) <'j'>: Set imm_reloc before p.
	<'1'>: New case.
	<'0'>: Use percent_op_null and don't set imm_reloc.
	<alu_op>: Handle *args == '1'.
	* testsuite/gas/riscv/tprel-add.d: New.
	* testsuite/gas/riscv/tprel-add.l: New.
	* testsuite/gas/riscv/tprel-add.s: New.
	opcodes/
	* riscv-opc.c (riscv_opcodes) <"add">: Use 1 not 0 for fourth arg.