x86: Support Intel Cherry Hill board

This adds support to Intel Cherry Hill board, a board based on
Intel Braswell SoC. The following devices are validated:

- serial port as the serial console
- on-board Realtek 8169 ethernet controller
- SATA AHCI controller
- EMMC/SDHC controller
- USB 3.0 xHCI controller
- PCIe x1 slot with a graphics card
- ICH SPI controller with an 8MB Macronix SPI flash
- Integrated graphics device as the video console

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>