MIPS: inst.h: define microMIPS sync op

The opcode for the sync instruction within POOL32AXf was missing. This
patch adds it for use by a subsequent patch.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>

arch/mips/include/uapi/asm/inst.h

@@ -303,6 +303,7 @@ enum mm_32axf_minor_op {
 	mm_tlbwr_op = 0x0cd,
 	mm_jalrs_op = 0x13c,
 	mm_jalrshb_op = 0x17c,
+	mm_sync_op = 0x1ad,
 	mm_syscall_op = 0x22d,
 	mm_eret_op = 0x3cd,
 };