dnsmasq: update homepage link

The doc.html seems like a better choice for a homepage link than the
list of files in the containing directory listing.

Cc: Matt Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit f9da847d93c061b2242547343cb4a707e8f1179d)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/dnsmasq/Config.in

@@ -4,7 +4,7 @@ config BR2_PACKAGE_DNSMASQ
 	  A lightweight DNS and DHCP server. It is intended to provide
 	  coupled DNS and DHCP service to a LAN.
 
-	  http://www.thekelleys.org.uk/dnsmasq/
+	  http://www.thekelleys.org.uk/dnsmasq/doc.html
 
 if BR2_PACKAGE_DNSMASQ