Input: i8042 - set up shared ps2_cmd_mutex for AUX ports

The commit 40974618 ("Input: i8042 - break load dependency ...")
correctly set up ps2_cmd_mutex pointer for the KBD port but forgot to do
the same for AUX port(s), which results in communication on KBD and AUX
ports to clash with each other.

Fixes: 40974618 ("Input: i8042 - break load dependency ...")
Reported-by: NBruno Wolff III <bruno@wolff.to>
Tested-by: NBruno Wolff III <bruno@wolff.to>
Cc: stable@vger.kernel.org
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/serio/i8042.c

@@ -1305,6 +1305,7 @@ static int __init i8042_create_aux_port(int idx)
 	serio->write		= i8042_aux_write;
 	serio->start		= i8042_start;
 	serio->stop		= i8042_stop;
+	serio->ps2_cmd_mutex	= &i8042_mutex;
 	serio->port_data	= port;
 	serio->dev.parent	= &i8042_platform_device->dev;
 	if (idx < 0) {