staging: brcm80211: replace si_* calls with ai_* calls in brcmsmac driver

The brcmsmac only supports chips with amba silicon interconnect so no
abstraction is required. The siutils functions will be removed from the
brcmsmac driver and this commit does easy replacement of siutils functions
that simply delegate to the corresponding aiutils function.

Reviewed-by: Henry Ptasinski <henryp@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>