x86: fsp: Save usable RAM and hob_list in the handoff area

x86: fsp: Save usable RAM and hob_list in the handoff area

The useable RAM is calculated when the RAM is inited. Save this value so
that it can be easily used in U-Boot proper.

Also save a pointer to the hob list so that it is accessible (before
relocation only) in U-Boot proper. This avoids having to scan it in SPL,
for everything U-Boot proper might need later.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: guard handoff_arch_save() with IS_ENABLED(CONFIG_USE_HOB)]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>