anv: fix ycbcr plane indexing with indirect descriptors
What does this MR do and why?
anv: fix ycbcr plane indexing with indirect descriptors
We need to add the plane index to compute the address from which to
load the descriptor (anv_sampled_image_descriptor in this case).
This was likely broken before we added direct descriptor support so
that gets a stable backport.
Cc: mesa-stable
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/11125
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>