[PATCH] libertas: remove adapter->{data,bcn}_avg_factor

Those two variables were initialized with some default values, but there
is no code that would ever change them. So we could use as well the defaults
directly.

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