staging: brcm80211: remove custom gpio support code

The custom gpio code is intended for hardware platform for specific
customers and require supporting functionality not included in the
fullmac driver. The fullmac driver does not need this so it has been
removed.

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>