mmc: davinci: add support for SDIO irq handling

This patch adds support for handling SDIO interrupt on DaVinci MMC/SD
controller.

The patch has been tested on DM355 and DA850 EVMs with Marvell Libertas
based SDIO wireless LAN card.

Signed-off-by: Alagu Sankar <alagusankar@embwise.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>