console: Use flush() before panic and reset

To make sure the panic and the reset messages will go out, console flush() should be used.
Sleep periods do not work in early u-boot phase when timer driver is not initialized yet.

Reference: https://lists.denx.de/pipermail/u-boot/2023-March/512233.html



Signed-off-by: Tony Dinh <mibodhi@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>