davinci: da8xx/omap-l1xx: Add EDMA platform data for da850/omap-l138

Currently da850/omap-l138 supports only one channel controller
instance of EDMA though EDMA driver as such supports multiple
channel controller instances. This patch adds platform data
for the 2nd EDMA channel controller. As, the platform data
differ between da830/omap-l137 and da850/omap-l138, existing
code has been re-shuffled to accommodate this.

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