staging: brcm80211: rename dhd_bus structure and functions

The header file dhd_bus.h contains several function prototypes
starting with dhd_bus_ and using parameter with struct dhd_bus.
These function and structure have been renamed to brcmf_bus.

Signed-off-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>