zink: fix sampler array collision in `nir_to_spirv`

zink: fix sampler array collision in `nir_to_spirv`

`nir_to_spirv` has flat arrays to map driver_location to sampler
variables.

Now when bindless textures are used together with non binless textures
the sampler vars are in different descriptor sets and the binding can be
the same between different descriptor sets, this causes a collision in
arrays.

This patches chamges `nir_to_spirv` to also index the array by whether
the texture is bindless.

Fixes: bc202553e9b ("zink: implement bindless textures")
Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22358>