tools: microcode-tool: Support parsing header file with a license block

The microcode header files in the Intel Chief River FSP package have
a license comment block. Update the microcode-tool to support parsing
it and extract the license text to the .dtsi file.

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