[PATCH] libertas: indirect all hardware access via hw_XXXX functions

This functions makes all libertas_sbi_XXX functions static to the
if_usb.c file and renames them to if_usb_XXXX(). The get called from
other places of the source code via priv->hw_XXXX().

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