x86: fsp: Support a warning message when DRAM init is slow

x86: fsp: Support a warning message when DRAM init is slow

With DDR4, Intel SOCs take quite a long time to init their memory. During
this time, if the user is watching, it looks like SPL has hung. Add a
message in this case.

This works by adding a return code to fspm_update_config() that indicates
whether MRC data was found and a new property to the device tree.

Also add one more debug message while starting.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
Tested-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>