kbuild, deb-pkg: improve Source field

The Source: field is defined as the source package in the package
archive from which a binary packages are built. As deb-pkg does not
generate a source package, we should avoid to use any existing source
packages here.
Signed-off-by: Frans Pop <elendil@planet.nl>
Acked-by: maximilian attems <max@stro.at>
Cc: Andres Salomon <dilinger@debian.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/package/builddeb

@@ -114,7 +114,7 @@ maintainer="$name <$email>"
 
 # Generate a simple changelog template
 cat <<EOF > debian/changelog
-linux ($packageversion) unstable; urgency=low
+linux-upstream ($packageversion) unstable; urgency=low
 
   * Custom built Linux kernel.
 
@@ -143,7 +143,7 @@ EOF
 
 # Generate a control file
 cat <<EOF > debian/control
-Source: linux
+Source: linux-upstream
 Section: base
 Priority: optional
 Maintainer: $maintainer