drivers/serial: Do not leave sysfs group in case of error in aspeed_vuart_probe()

There are several error handling paths in aspeed_vuart_probe(),
where sysfs group is left unremoved. The patch fixes them.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>