ap51-flash: Fix source repository URL

The URL git://dev.cloudtrax.com/ap51-flash.git is not the actual public
source repository URL for ap51-flash. It is not even accessible in the
moment. The official repository can now be found at github.

Signed-off-by: Sven Eckelmann <sven@narfation.org>

utils/ap51-flash/Makefile

@@ -11,7 +11,7 @@ PKG_VERSION:=2017-12-07
 PKG_RELEASE:=1
 
 PKG_SOURCE_PROTO:=git
-PKG_SOURCE_URL:=git://dev.cloudtrax.com/ap51-flash.git
+PKG_SOURCE_URL:=https://github.com/ap51-flash/ap51-flash.git
 PKG_SOURCE_SUBDIR:=$(PKG_NAME)-$(PKG_VERSION)
 PKG_SOURCE_VERSION:=f94f9c99711d14a3c0186318d822d67d9d0ce391
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION)-$(PKG_SOURCE_VERSION).tar.xz