package/matchbox-panel: add an upstream URL to Config.in

Add an upstream URL to the help text in Config.in. This
addresses the 'Missing' URL status in the package stats
web page output.

Signed-off-by: Mark Corbin <mark@dibsco.co.uk>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 484b687f79d06945c581cdaf709c2ecd8cbb3774)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/matchbox-panel/Config.in

@@ -4,3 +4,5 @@ config BR2_PACKAGE_MATCHBOX_PANEL
 	help
 	  A flexible always present 'window bar' for holding
 	  application launchers.
+
+	  http://git.yoctoproject.org/cgit/cgit.cgi/matchbox-panel/