serial: samsung: Change barrier() to cpu_relax() in console output

The two functions to write out to the console (one used in normal
console mode and one in polling console mode) were slightly different.
One used a barrier() in its loop and the other a cpu_relax().  The
barrier() really doesn't do anything since we're using rd_regl() to
read the port anyway.  Switch it to cpu_relax() to make things
consistent.

No known bugs / issues are fixed by this change--it just makes things
more consistent.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>