package/dt: fix Kconfig package URL

The old package URL is no longer working. This commit updates it to
the one advertised at [1].

[1] https://github.com/RobinTMiller/dt/blob/b30eb7a123cfba900f26ceda413ea8ae49c3817e/html/dt.html#L33

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/dt/Config.in

@@ -18,4 +18,4 @@ config BR2_PACKAGE_DT
 	  before exiting. Since verification of data is performed,
 	  dt can be thought of as a generic diagnostic tool.
 
-	  http://www.scsifaq.org/RMiller_Tools/dt.html
+	  https://github.com/RobinTMiller/dt