Adds AM33XX MMC support for am335x-bone, am335x-evm and am335x-evmsk boards.

Also added is the DMA binding definitions based on the generic DMA request
binding.

Additional changes made to DTS:
* Interrupt, reg and compatible properties added
* ti,needs-special-hs-handling added
Signed-off-by: NMatt Porter <mporter@ti.com>
Acked-by: NTony Lindgren <tony@atomide.com>
Signed-off-by: NJoel Fernandes <joelf@ti.com>
Signed-off-by: NBenoit Cousson <bcousson@baylibre.com>