Sync logic with Linux kernel where TX empty flag is checked before char
is sent.
This logic is fixing problem with console on zynqmp platform.
For example:
DRAM: 2 GiB
Enabling Caches...
EL Level: �� sdhci@ff170000: 0
Using default environment
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Moritz Fischer <moritz.fischer@ettus.com>