Skip double FIFO probing in com(4)

[Marcus Glocker]

If a FIFO device already got a FIFO depth assigned, don't run a FIFO
probe against it.

ok?


Index: dev/ic/com.c
===================================================================
RCS file: /cvs/src/sys/dev/ic/com.c,v
retrieving revision 1.159
diff -u -p -r1.159 com.c
--- dev/ic/com.c        16 Aug 2016 08:15:04 -0000      1.159
+++ dev/ic/com.c        17 Aug 2016 13:31:47 -0000
@@ -1855,7 +1855,7 @@ com_fifo_probe(struct com_softc *sc)
        u_int8_t fifo, ier;
        int timo, len;
 
-       if (!ISSET(sc->sc_hwflags, COM_HW_FIFO))
+       if (!ISSET(sc->sc_hwflags, COM_HW_FIFO) || sc->sc_fifolen)
                return;
 
        ier = 0;