package/mksh: fix project URL in Config.in

It's http://www.mirbsd.org/mksh.htm

Signed-off-by: Carlos Santos <unixmania@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 399ad854cc210db728e06933b8a4ad9089176ec1)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/mksh/Config.in

@@ -22,4 +22,4 @@ config BR2_PACKAGE_MKSH
 	  operating environments
 	  (thus including patches from pdksh on e.g. Debian).
 
-	  http://mirbsd.de/mksh
+	  http://www.mirbsd.org/mksh.htm