arch/arm/dts: Add Turris Omnia device tree

This device tree is taken from mainline Linux kernel commit
7b7db5ab. Added is also a -u-boot.dtsi file with these additions:

  - aliases for I2C and SPI devices are added, because i2cmux and
    SPI flash doesn't work otherwise
  - spi_flash node has been added so that the new DM API works
  - the ATSHA204A node is added in the i2c@5 node
  - "u-boot,dm-pre-reloc"s are added in needed nodes for SPL
    build to work correctly

Signed-off-by: Marek Behun <marek.behun@nic.cz>

 create mode 100644 arch/arm/dts/armada-385-turris-omnia-u-boot.dtsi
 create mode 100644 arch/arm/dts/armada-385-turris-omnia.dts
Signed-off-by: Stefan Roese <sr@denx.de>