mmc: omap: enable high capacity

Enable high capacity to host capability.
Fixes eMMC detection on boot from MMC/SD card.

Signed-off-by: Balaji T K <balajitk@ti.com>
Signed-off-by: Aneesh V <aneesh@ti.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>