The vtn_ssa_value for a cmat is not backed by a nir_def, but by a nir_variable, so
can't be used directly when calling a function. In most cases the cmat is used by
reference so code will take the value of deref for it (which is a `nir_def`).
When passing a cooperative matrix to a function by value, let the caller pass the deref
value, and the callee copy to a new local variable from that deref.
Fixes: b98f87612b ("spirv: Implement SPV_KHR_cooperative_matrix")
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34364>
(cherry picked from commit 0cad7b0968)
4bb8d70fd6