DMA: Freescale: Add new 8-channel DMA engine device tree nodes

Freescale QorIQ T4 and B4 introduce new 8-channel DMA engines, this patch adds
the device tree nodes for them.

Signed-off-by: Hongbo Zhang <hongbo.zhang@freescale.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>