5c: fix pc recalculation in the presence of AFUNCDATA

This makes CL 11683043 not break arm anymore.

R=golang-dev, bradfitz, dave
CC=golang-dev
https://golang.org/cl/11888043

src/cmd/5c/reg.c

@@ -461,6 +461,7 @@ brk:
 			case AGLOBL:
 			case ANAME:
 			case ASIGNAME:
+			case AFUNCDATA:
 				break;
 			}
 		}