DaVinci: EDMA: Updating terminlogy in EDMA driver

The patch itself does not change the functionality of
any existing code. PARAM entries in the present GIT kernel
are referred to as slots. New API's being added to the
EDMA driver were referring to these PARAM entries as
"params". This patch updates the terminolgy used in the
EDMA driver.

Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>