mmc: sh_mmcif: Support MMC_SLEEP_AWAKE command

The MMC_SLEEP_AWAKE and SD_IO_SEND_OP_COND commands share the same
opcode. SD_IO_SEND_OP_COND isn't supported by the SH MMCIF, but
MMC_SLEEP_AWAKE is. Discriminate between the two commands using the
command flags, and reject SD_IO_SEND_OP_COND only.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Chris Ball <cjb@laptop.org>