staging: brcm80211: move waitqueue code to dhd_sdio.c

In fullmac waitqueue for tx control is used by bus interface layer
only. So move the related code to dhd_sdio.c

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