serial: 8520_ce4100: Reuse mem_serial_in() in ce4100_mem_serial_in()

serial: 8520_ce4100: Reuse mem_serial_in() in ce4100_mem_serial_in()

In one place in ce4100_mem_serial_in() the code may be replaced with
mem_serial_in() call. Do it so and collapse two conditionals into one.

Suggested-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250701134200.2621898-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>