serial: max3100: Lock port->lock when calling uart_handle_cts_change()

serial: max3100: Lock port->lock when calling uart_handle_cts_change()

[ Upstream commit 77ab53371a2066fdf9b895246505f5ef5a4b5d47 ]

uart_handle_cts_change() has to be called with port lock taken,
Since we run it in a separate work, the lock may not be taken at
the time of running. Make sure that it's taken by explicitly doing
that. Without it we got a splat:

  WARNING: CPU: 0 PID: 10 at drivers/tty/serial/serial_core.c:3491 uart_handle_cts_change+0xa6/0xb0
  ...
  Workqueue: max3100-0 max3100_work [max3100]
  RIP: 0010:uart_handle_cts_change+0xa6/0xb0
  ...
   max3100_handlerx+0xc5/0x110 [max3100]
   max3100_work+0x12a/0x340 [max3100]

Fixes: 7831d56b0a35 ("tty: MAX3100")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240402195306.269276-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>