pcnet: Clear ERR in CSR0 on stop

pcnet_stop already clears any reason (BABL, CERR, MISS, MERR) why ERR
(bit 15) should be set in CRS0. So we have to clear that bit as well.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

hw/pcnet.c

@@ -884,7 +884,7 @@ static void pcnet_stop(PCNetState *s)
 #ifdef PCNET_DEBUG
     printf("pcnet_stop\n");
 #endif
-    s->csr[0] &= ~0x7feb;
+    s->csr[0] &= ~0xffeb;
     s->csr[0] |= 0x0014;
     s->csr[4] &= ~0x02c2;
     s->csr[5] &= ~0x0011;