video: Use cyclic to handle video sync

video: Use cyclic to handle video sync

At present U-Boot flushes the cache after every character written to
the display. This makes the command-line slower, to the point that
pasting in long strings can fail.

Add a cyclic function to sync the display every 10ms. Enable this by
default.

Allow much longer times for sandbox, since the SDL display is quite
slow.

Avoid size growth if the feature is disabled by making the new init and
destroy functions dependent on CYCLIC being enabled.

Signed-off-by: Simon Glass <sjg@chromium.org>