linux: remove dirs dependency

The "dirs" dependency is redundant because now the "generic-package"
infrastructure add automatically the "dirs" dependency so just remove
the redundant references.

Signed-off-by: Fabio Porcedda <fabio.porcedda@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>