package/libupnp: disable blocking-tcp

Suggested by Gerbera:
https://github.com/gerbera/gerbera/commit/fcf31472239705e7d28af81cbe326f8f416f7f7d

CMake Warning at CMakeLists.txt:583 (message):
  !! It is strongly recommended to build libupnp with --disable-blocking-tcp-connections !!
  Without this option non-responsive control points can cause libupnp to hang.

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libupnp/libupnp.mk

@@ -17,6 +17,7 @@ LIBUPNP_DEPENDENCIES = host-pkgconf
 
 # Bind the internal miniserver socket with reuseaddr to allow clean restarts.
 LIBUPNP_CONF_OPTS += \
+	--disable-blocking-tcp-connections \
 	--disable-samples \
 	--enable-reuseaddr