brcm80211: smac: use inline access functions for struct si_pub fields

Instead of directly accessing the fields in struct si_pub the driver
now uses inline access functions. This is in preparation of the bcma
integration as a lot of information will be provided by bcma module.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Alwin Beukers <alwin@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>