boot/uboot: add an upstream URL to Config.in

Add an upstream URL to the help text in Config.in. This
addresses the issue where an incorrect URL is displayed
on the package stats web page.

Signed-off-by: Mark Corbin <mark@dibsco.co.uk>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

boot/uboot/Config.in

@@ -3,6 +3,8 @@ config BR2_TARGET_UBOOT
 	help
 	  Build "Das U-Boot" Boot Monitor
 
+	  https://www.denx.de/wiki/U-Boot
+
 if BR2_TARGET_UBOOT
 choice
 	prompt "Build system"