media: atomisp: Fix use after free in atomisp_alloc_css_stat_bufs()

The "s3a_buf" is freed along with all the other items on the
"asd->s3a_stats" list.  It leads to a double free and a use after free.

Link: https://lore.kernel.org/linux-media/X9dSO3RGf7r0pq2k@mwanda


Fixes: ad85094b ("Revert "media: staging: atomisp: Remove driver"")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>