ARM: dts: keystone: enable accumulator channels

Add low priority accumulator channel that can monitor multiple QMSS
queues. User for example could use the accumular queue for Netcp
Rx completion. While at it, also add an extra line end of each top
level node in DTS to make it more readable.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>