davinci: add EDMA driver

Original code for 2.6.10 and 2.6.28 series done by Texas Instruments
and MontaVista, but major updates and rework done by Troy Kisky and
David Brownell.

Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Cc: Troy Kisky <troy.kisky@boundarydevices.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>