Revert "plat: dma: increase dma priority"

This causes the touchscreen to become less responsive under system load.

This reverts commit 426e0af03c9feabf26cc6b3086bb1da1c301e0bb.

Change-Id: I05cdd6c64641dcb100c0c45dd88f96753dca53ac
Merge branch 'encore-omap3-3' into encore-omap3-3.0.y