ARM: dts: dra7: Use eDMA and add DAT port address for McASP3

McASP3 does not support constant addressing mode on the DAT
port, so increment transfers must be used instead.  This
restriction is also applicable for McASP1 and McASP2.

This DMA addressing constraint poses a major problem for sDMA
where constant addressing mode is used on the peripheral side.
Unfortunately, using increment transfers in sDMA comes with
important side effects.

The addressing mode used in eDMA is INC, so the silicon limitation
described above has no impact and the McASP3 DAT port can be
safely added by switching to eDMA instead of sDMA.

Signed-off-by: Misael Lopez Cruz <misael.lopez@ti.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>