cmd/compile: add OMOD to list of ops that might panic

Follow-up to CL 32551.

Change-Id: If68f9581a7f13e04796aaff2007c09f8ea2c3611
Reviewed-on: https://go-review.googlesource.com/32586
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/gc/subr.go

@@ -1183,7 +1183,7 @@ func ullmancalc(n *Node) {
 			goto out
 		}
 	case OINDEX, OSLICE, OSLICEARR, OSLICE3, OSLICE3ARR, OSLICESTR,
-		OIND, ODOTPTR, ODOTTYPE, ODIV:
+		OIND, ODOTPTR, ODOTTYPE, ODIV, OMOD:
 		// These ops might panic, make sure they are done
 		// before we start marshaling args for a call. See issue 16760.
 		ul = UINF