ARM: edma: Get IP configuration from HW (number of channels, tc, etc)

From CCCFG register of eDMA3 we can get all the needed information for the
driver about the IP:
Number of channels: NUM_DMACH
Number of regions: NUM_REGN
Number of slots (PaRAM sets): NUM_PAENTRY
Number of TC/EQ: NUM_EVQUE

In case when booted with DT or the queue_priority_mapping is not provided
set up a default priority map.

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