serial: owl: drop low-latency workaround

serial: owl: drop low-latency workaround

The owl driver has always carried an unnecessary workaround for the
infamous low_latency behaviour of tty_flip_buffer_push(), which had
been removed years before the driver was added by commit d4bd602dedaf
("tty: serial: owl: Implement console driver").

Specifically, since commit 671ac8a2b918 ("tty: Fix low_latency BUG"),
tty_flip_buffer_push() always schedules a work item to push data to the
line discipline and there's no need to keep any low_latency hacks around.

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210421095509.3024-18-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>