package/elf2flt: add an upstream URL to Config.in.host

Add an upstream URL to the help text in Config.in.host. This
addresses the 'Missing' URL status in the package stats
web page output.

Signed-off-by: Mark Corbin <mark@dibsco.co.uk>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/elf2flt/Config.in.host

@@ -9,3 +9,5 @@ config BR2_PACKAGE_HOST_ELF2FLT
 
 	  This option compiles the required tools and makes the required
 	  modifications on your toolchain (linker).
+
+	  https://github.com/uclinux-dev/elf2flt