x86: Add congatec conga-QA3/E3845-4G (Bay Trail) support

This patch adds support for the congatec conga-QA3/E3845-4G eMMC8 SoM,
installed on the congatec Qseven 2.0 evaluation carrier board
(conga-QEVAL).

Its port is very similar to the MinnowboardMAX port and also uses
the Intel FSP as described in doc/README.x86.

Currently supported are the following interfaces / devices:
- UART (via Winbond legacy SuperIO chip on carrier board)
- Ethernet (PCIe Intel I210 / E1000)
- SPI including SPI NOR as boot-device
- USB 2.0
- SATA via U-Boot SCSI IF
- eMMC
- Video (HDMI output @ 800x600)
- PCIe

Not supported yet is:
- I2C
- USB 3.0

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>