gbproxy: Replace ';;' by ';'

This patch removes some superfluous ';' from the code.

Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/gprs/gprs_gb_parse.c b/openbsc/src/gprs/gprs_gb_parse.c
index db40e97..87cea1b 100644
--- a/openbsc/src/gprs/gprs_gb_parse.c
+++ b/openbsc/src/gprs/gprs_gb_parse.c
@@ -157,7 +157,7 @@
 	if (lv_shift(&data, &data_len, NULL, &value_len) <= 0 ||
 	    value_len < 1 || value_len > 8)
 		/* invalid */
-		return 0;;
+		return 0;
 
 	/* Skip Attach type */
 	/* Skip Ciphering key sequence number */
@@ -421,7 +421,7 @@
 	if (lv_shift(&data, &data_len, NULL, &value_len) <= 0 ||
 	    value_len < 4 || value_len > 14)
 		/* invalid */
-		return 0;;
+		return 0;
 
 	/* Skip Requested PDP address */
 	if (lv_shift(&data, &data_len, NULL, &value_len) <= 0 ||