kbuild, deb-pkg: minor general improvements in builddeb script

Minor coding style improvements and typo fix in leading comment.

Signed-off-by: Frans Pop <elendil@planet.nl>
Cc: Andres Salomon <dilinger@debian.org>
Acked-by: maximilian attems <max@stro.at>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>