mvebu: 6.6: Backport Turris Omnia MCU patches from 6.11

mvebu: 6.6: Backport Turris Omnia MCU patches from 6.11

This backports patches
  dt-bindings: firmware: add cznic,turris-omnia-mcu binding
  platform: cznic: Add preliminary support for Turris Omnia MCU
  platform: cznic: turris-omnia-mcu: Add support for MCU connected GPIOs
  platform: cznic: turris-omnia-mcu: Add support for poweroff and wakeup
  platform: cznic: turris-omnia-mcu: Add support for MCU watchdog
  platform: cznic: turris-omnia-mcu: Add support for MCU provided TRNG
  ARM: dts: turris-omnia: Add MCU system-controller node
  ARM: dts: turris-omnia: Add GPIO key node for front button
  platform: cznic: turris-omnia-mcu: Depend on OF
  platform: cznic: turris-omnia-mcu: Depend on WATCHDOG
  platform: cznic: turris-omnia-mcu: fix Kconfig dependencies
that will be released in 6.11 into mvebu/patches-6.6.

Signed-off-by: Marek Behún <kabel@kernel.org>
Link: https://github.com/openwrt/openwrt/pull/13799
Signed-off-by: Robert Marko <robimarko@gmail.com>