chromebook_link: Enable the copy framebuffer

Update the video driver to support this feature and enable it on link.
Also remove the multi-line scrolling since normal scrolling is fast enough
now.

With this change, the time taken to print the environment to the display
without CONFIG_CONSOLE_SCROLL_LINES is reduced from about 930ms to 29ms.

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