radeon/vcn/vp9: search the render target from the whole list

The number of render targets could be more than max of references,
so we search the full list of the render pictures for the current
render target index

https://bugs.freedesktop.org/show_bug.cgi?id=109648



Signed-off-by: Leo Liu <leo.liu@amd.com>
Tested-by: James Zhu <James.Zhu@amd.com>
Acked-by: James <Zhu&lt;James.Zhu@amd.com>
Cc: <mesa-stable@lists.freedesktop.org>
(cherry picked from commit d4e0fbc9)