imx: add imx8x capricorn giedi board

Add support for i.MX8X based Capricorn Giedi SoM.

Supported interfaces: GPIO, ENET, eMMC, I2C, UART.

Console output:

  U-Boot SPL 2020.01-00003-gfd1c98f (Jan 07 2020 - 15:51:25 +0100)
  Trying to boot from MMC1
  Load image from MMC/SD 0x3e400

  U-Boot 2020.01-00003-gfd1c98f (Jan 07 2020 - 15:51:25 +0100) ##v01.07

  CPU:   NXP i.MX8QXP RevB A35 at 1200 MHz at 30C

  Model: Siemens Giedi
  Board: Capricorn
  Boot:  MMC0
  DRAM:  1022 MiB
  MMC:   FSL_SDHC: 0
  Loading Environment from MMC... OK
  In:    serial@5a080000
  Out:   serial@5a080000
  Err:   serial@5a080000
  Net:   eth1: ethernet@5b050000 [PRIME]
  Autobooting in 1 seconds, press "<Esc><Esc>" to stop

Signed-off-by: Anatolij Gustschin <agust@denx.de>