ARM: edma: Take the number of tc from edma_soc_info (pdata)

Instead of saving the for loop length, take the num_tc value from the pdata.
In case of DT boot set the n_tc to 3 as it is hardwired in edma_of_parse_dt()
This is a temporary state since upcoming patch(es) will change how we are
dealing with these parameters.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>