kbuild: make deb-pkg - add 'Provides:' line

http://bugzilla.kernel.org/show_bug.cgi?id=8941

Current Debian's kernel-modules depend on matching linux-image-$version, though
Linux's make deb-pkg build a .deb that 'Provides: kernel-image-$version' only.
The following patch adds the Debian-compliant 'Provides', leaving the default
one; hopely this will make way all happy.

Signed-off-by: paolo <oopla@users.sf.net>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>