staging: brcm80211: sdh related code cleanup

Gave struct brcmf_sdio the more applicable name 'brcmf_sdio_card'. Enforced
stronger type checking by replacing void *sdh by struct brcmf_sdio_card *.

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