libertas: remove arbitrary typedefs

New typedefs are usually frowned upon. This patch changes
libertas_adapter -> struct libertas_adapter
libertas_priv -> struct libertas_priv

While passing, make everything checkpatch.pl-clean that gets touches.

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>