OMAP: hwmod data: Add dev_attr and use in the host driver

Add a device attribute to hwmod data of omap2430, omap3, omap4.
Currently the device attribute holds information regarding dual volt MMC card
support by the controller which will be later passed to the host driver via
platform data.

Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Kishore Kadiyala <kishore.kadiyala@ti.com>
Acked-by: Benoit Cousson<b-cousson@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>