mmc: skip select_mode_and_width for MMC SPI host

The MMC mode and width are fixed for MMC SPI host hence we skip
sd_select_mode_and_width() and mmc_select_mode_and_width() for
MMC SPI host.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>