vfio/pds: Fix memory leak in pds_vfio_dirty_enable()

vfio/pds: Fix memory leak in pds_vfio_dirty_enable()

pds_vfio_dirty_enable() allocates memory for region_info. If
interval_tree_iter_first() returns NULL, the function returns -EINVAL
immediately without freeing the allocated memory, causing a memory leak.

Fix this by jumping to the out_free_region_info label to ensure
region_info is freed.

Fixes: 2e7c6feb4ef52 ("vfio/pds: Add multi-region support")
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Link: https://lore.kernel.org/r/20251225143150.1117366-1-zilin@seu.edu.cn
Signed-off-by: Alex Williamson <alex@shazbot.org>