serial: pch_uart: CIRC_CNT_TO_END() is enough

Testing also CIRC_CNT() with CIRC_CNT_TO_END() is unnecessary because
to latter alone covers all necessary cases.

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220823141839.165244-3-ilpo.jarvinen@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>