OMAP2+: DMA: hwmod: Device registration

Prepare OMAP2+ DMA to use hwmod infrastructure so that DMA can register
as platform device.

Signed-off-by: G, Manjunath Kondaiah <manjugk@ti.com>
Tested-by: Kevin Hilman <khilman@deeprootsystems.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>