io:core: In iio_map_array_register() cleanup in case of error

In function iio_map_array_register() properly rewind in case of error.

Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/1606571059-13974-2-git-send-email-LinoSanfilippo@gmx.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>