radv: set combinedImageSamplerDescriptorCount to 1 for multi-planar formats

radv: set combinedImageSamplerDescriptorCount to 1 for multi-planar formats

RADV compacts all descriptors for multi-planar images into one
combined image sampler, so it should be 96, and not eg. 192 for a two
planes format.

Fixes new CTS
dEQP-VK.binding_model.descriptor_buffer.ycbcr_sampler.*array.

Cc: mesa-stable
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26498>
(cherry picked from commit 3678482f1e834cd12b17fd0bbd18d7ba2de34a9f)