x86: timer: Set up the timer in timer_early_get_count()

This function can be called before the timer is set up. Make sure that the
init function is called so that it works correctly.

This is needed so that bootstage can work correctly in TPL.

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