androiddump: fix leak on --extcap-interfaces

extcap_base_register_interface duplicates the memory, so there is no
need to keep it around.

Change-Id: I2bac8be519b659504c512d4eb29be8f7ef6dbd59
Reviewed-on: https://code.wireshark.org/review/15919
Reviewed-by: Anders Broman <a.broman58@gmail.com>

extcap/androiddump.c

@@ -627,6 +627,8 @@ static void new_interface(extcap_parameters * extcap_conf, const gchar *interfac
     } else if (is_specified_interface(interface, INTERFACE_ANDROID_WIFI_TCPDUMP)) {
         extcap_base_register_interface(extcap_conf, interface, ifdisplay, 1, "Ethernet");
     }
+    g_free(interface);
+    g_free(ifdisplay);
 }