greybus: uart: remove the redundant unregister chrdev

The unregister_chrdev_region() does twice here.
The chrdev region was unregistered
inside tty_unregister_driver().
Signed-off-by: Phong Tran <tranmanphong@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/uart.c

@@ -732,12 +732,8 @@ static int gb_tty_init(void)
 
 static void gb_tty_exit(void)
 {
-	int major = MAJOR(gb_tty_driver->major);
-	int minor = gb_tty_driver->minor_start;
-
 	tty_unregister_driver(gb_tty_driver);
 	put_tty_driver(gb_tty_driver);
-	unregister_chrdev_region(MKDEV(major, minor), GB_NUM_MINORS);
 }
 
 static struct gb_protocol uart_protocol = {