x86: Add a comment for board_init_f_r_trampoline()

Add a comment for this function in the header.

Change the function (and the one after) to use __noreturn to keep
checkpatch happy.

Add docs to board_init_f_r() while we are here.

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