ARM: OMAP2+: Configure dma_plat_info directly and drop dma_dev_attr

Let's prepare things for passing dma_plat_info to the dmaengine driver in
device tree auxdata. To do that, we want to configure dma_plat_info
directly. And we can also drop the related dma_dev_attr data.

Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Vinod Koul <vkoul@kernel.org>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>