brcmfmac: fix brcmf_sdcard_send_pkt() for host without sg support

If the host does not support scatter-gather transmit the packets
in the pktq individually using brcmf_sdio_buffrw().

Reviewed-by: Franky Lin <frankyl@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>