vfio/pds: replace bitmap_free with vfree

vfio/pds: replace bitmap_free with vfree

host_seq_bmp is allocated with vzalloc but is currently freed with
bitmap_free, which uses kfree internally. This mismach prevents the
resource from being released properly and may result in memory leaks
or other issues.

Fix this by freeing host_seq_bmp with vfree to match the vzalloc
allocation.

Fixes: f232836a9152 ("vfio/pds: Add support for dirty page tracking")
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
Link: https://lore.kernel.org/r/20250913153154.1028835-1-zilin@seu.edu.cn
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>