dts: arm: socfpga: merge gen5 devicetrees from linux

dts: arm: socfpga: merge gen5 devicetrees from linux

Add -u-boot.dtsi files to keep the current U-Boot behaviour:
- add u-boot,dm-pre-reloc where required
- disable watchdog
- set uart clock frequency
- add gpio bank-name properties
where appropriate:
- make qspi work (add alias for spi0, fix compatible for flash)
- enable usb (status okay, add alias for udc0)

Adapt board dts files that are not in Linux to keep their old
behaviour.

Change licenses to SPDX.

(Patman warnings/errors are in 1:1 copied files from Linux)

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>