depmod: Use strbuf for dependency output

depmod: Use strbuf for dependency output

Use shared/strbuf instead of manually re-implementing its features.
Reduces the amount of custom code in depmod, simplifies auditing,
reduces binary size, and has the nice benefit of slightly faster
runtime due to memory reusage.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/193
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>