P2P: add a missing 'return' after building IE from an empty string

When building IE from an empty string and CONFIG_WPS_STRICT is
not defined, redundant 2 bytes are being added to the string.

We have to return right after building the "dummy" string.

Signed-off-by: Eliad Peller <eliad@wizery.com>

src/p2p/p2p_build.c

@@ -346,6 +346,7 @@ static void p2p_add_wps_string(struct wpabuf *buf, enum wps_attribute attr,
 		 */
 		wpabuf_put_be16(buf, 1);
 		wpabuf_put_u8(buf, ' ');
+		return;
 	}
 #endif /* CONFIG_WPS_STRICT */
 	wpabuf_put_be16(buf, len);