DaVinci: EDMA: Fix Bug in edma_alloc_cont_slots API

The edma_alloc_cont_slots API is used for obtaining a set of
contiguous slots. When we use the "_ANY" option with this
API, by definition of this option it is suppossed to start
looking for a set of contiguous slots starting from slot 64 for
DaVinci SOC's and 32 for DA8xx SOC's. This has been explained in
the API description in the driver itself. So when we use the
"_ANY" option with this API, the slot number passed as
an argument should be a "don't care".
This patch takes care of this condition mentioned above.
When checking to see if the starting slot is a valid number,
it checks to make sure that the "_ANY" option is not used.

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