Use the Kernel devicetrees

[pamolloy]

We should use the Linux kernel devicetrees and not maintain separate ones in U-Boot. Take extra care with handling bootph-pre-ram.

[pamolloy]

CC @gmalysa

[gmalysa]

Eventually yes, but they'll need to be available in mainline linux and not just the ADI fork, and then we can use OF_UPSTREAM to handle the device trees + have a small overlay if need be for bootph-pre-ram or other small changes. We should probably also audit those properties to see if they are actually necessary or if we just added them defensively, especially with regards to SPL.