x86: Rename existing FSP code to fsp1

x86: Rename existing FSP code to fsp1

Since there is now a new version of the FSP and it is incompatible with
the existing version, move the code into an fsp1 directory. This will
allow us to put FSP v2 code into an fsp2 directory.

Add a Kconfig which defines which version is in use.

Some of the code in this new fsp1/ directory is generic across both FSPv1
and FSPv2. Future patches will address this.

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