ARM: OMAP: hsmmc: Add support for AM3517EVM base-board MMC slot

Add support for base-board MMC slot

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Abhilash K V <abhilash.kv@ti.com>
[tony@atomide.com: updated subject]
Signed-off-by: Tony Lindgren <tony@atomide.com>