mvebu dt for 4.20 (part 1)

- updates the armada-xp-98dx3236 SoC and related boards to use the new
  style dts bindings for nand

- add db-88f6820-amc board: plugin card for some of Marvell's switch
  development kits

- fix SPI and I2C bus warnings coming with the new checks in dtc

- add new compatible string "marvell,prestera" to the armada-xp-98dx*

- fix sdhci supply property name on the clearfog (the '-supply' suffix
  was missing)

* tag 'mvebu-dt-4.20-1' of git://git.infradead.org/linux-mvebu:
  ARM: dts: clearfog: fix sdhci supply property name
  ARM: dts: mvebu: add "marvell,prestera" to PP nodes
  ARM: dts: marvell: Fix SPI and I2C bus warnings
  ARM: dts: mvebu: Add device tree for db-88f6820-amc board
  ARM: dts: mvebu: db-xc3-24g4: use new style nand binding
  ARM: dts: mvebu: db-dxbc2: use new style nand binding
  ARM: dts: mvebu: 98dx3236: Rename nand controller node
Signed-off-by: Arnd Bergmann <arnd@arndb.de>