ARM: dts: NSP: Add dma-coherent to relevant DT entries

Cache related issues with DMA rings and performance issues related to
caching are being caused by not properly setting the "dma-coherent" flag
in the device tree entries.  Adding it here to correct the issue.

Signed-off-by: Jon Mason <jon.mason@broadcom.com>
Fixes: 3107fa5b ("ARM: dts: NSP: Add SD/MMC support")
Fixes: 13d04f20 ("ARM: dts: NSP: Add AMAC entries")
Fixes: 5aeda7bf ("ARM: dts: NSP: Add and enable amac2")
Fixes: 17d51717 ("ARM: dts: NSP: Add mailbox (PDC) to NSP")
Fixes: 1d8ece66 ("ARM: dts: NSP: Add EHCI/OHCI USB nodes to device tree")
Fixes: 0f9f27a3 ("ARM: dts: NSP: Add I2C support to the DT")
Fixes: 8dbcad02 ("ARM: dts: nsp: Add sata device tree entry")
Fixes: 52219902 ("ARM: dts: NSP: Fix PCIE DT issue")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>