davinci: Fix edma_alloc_channel api for EDMA_CHANNEL_ANY case

Though edma_alloc_channel api was looping through the available
channel controllers in EDMA_CHANNEL_ANY case, it was never
returning the channel for 2nd channel controller, if 1st
channel controller had no free channels. This issue has
been fixed with this patch.

Signed-off-by: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>