ir3/nir: Set up image_dims consts for image_deref_size intrinsic too

ir3/nir: Set up image_dims consts for image_deref_size intrinsic too

`nir_intrinsic_image_deref_size` is not being considered during scan for
driver constants, so image constants are not emitted if a shader
only ever query the size of an image (no load, store, atomic op, etc).
This is unlikely, but possible.

Reviewed-by: Rob Clark <robdclark@gmail.com>