staging: brcm80211: remove dependency between aiutils and siutils sources

The two source files have been separated where aiutils is only used
by the brcmsmac driver and the siutils is only used by the brcmfmac
driver.

Cc: devel@linuxdriverproject.org
Cc: linux-wireless@vger.kernel.org
Cc: Brett Rudley <brudley@broadcom.com>
Cc: Henry Ptasinski <henryp@broadcom.com>
Cc: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>