sgsn: Comparing array to NULL is not useful

.v is a unsigned char array with up-to 255 elements. We do not
need to add a null check here.

Fixes: Coverity CID 1040719
diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index f7a5cde..6ba3855 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -1221,7 +1221,7 @@
 	pdp->lib->eua.v[0] |= 0xf0;
 
 	/* Optional: Protocol configuration options (FIXME: why 'req') */
-	if (pdp->lib->pco_req.l && pdp->lib->pco_req.v)
+	if (pdp->lib->pco_req.l)
 		msgb_tlv_put(msg, GSM48_IE_GSM_PROTO_CONF_OPT,
 			     pdp->lib->pco_req.l, pdp->lib->pco_req.v);