serial: 8250: rename unlock labels

Rename a couple of oddly named labels that are used to unlock before
returning after what they do (rather than after the context they are
used in) to improve readability.

Tested-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20211015111422.1027-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>