MIPS: Actually decode JALX in `__compute_return_epc_for_insn'

commit a9db101b735a9d49295326ae41f610f6da62b08c upstream.

Complement commit fb6883e ("MIPS: microMIPS: Support handling of
delay slots.") and actually decode the regular MIPS JALX major
instruction opcode, the handling of which has been added with the said
commit for EPC calculation in `__compute_return_epc_for_insn'.

Fixes: fb6883e ("MIPS: microMIPS: Support handling of delay slots.")
Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16394/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Maciej W. Rozycki

arch/mips/kernel/branch.c

@@ -556,6 +556,7 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
 	/*
 	 * These are unconditional and in j_format.
 	 */
+	case jalx_op:
 	case jal_op:
 		regs->regs[31] = regs->cp0_epc + 8;
 	case j_op: