mmc: omap: Fix DMA configuration to not rely on device id

We are wrongly relying on device id for the DMA configuration
which can lead to wrong DMA channel being selected.

Fix the issue by using the standard resources like we should.

Cc: linux-mmc@vger.kernel.org
Acked-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>