serial: xilinx_uartps: Fix kernel doc about .remove()'s return code

serial: xilinx_uartps: Fix kernel doc about .remove()'s return code

Since the driver was converted to use .remove_new() the return function
doesn't return a value any more. So remove the obsolete documentation
about the return value.

Reported-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/20231117101236.878008-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>