x86: conga-qeval20-qa3: Add README to explain the console UART options

This patch adds a small README to explain the 2 defconfig files and its
usage for the different console UART options.

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