nir: add a cmat call instruction type.

This adds a new instruction type to handle cooperative matrix calls.

This clones the call instr, drops callee, and adds a single metadata
slot and a call operation (dummy only for now).

(Not NACKed by Alyssa)

Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38389>

src/broadcom/compiler/vir.c

@@ -1348,6 +1348,7 @@ v3d_instr_delay_cb(nir_instr *instr, void *data)
    case nir_instr_type_deref:
    case nir_instr_type_jump:
    case nir_instr_type_call:
+   case nir_instr_type_cmat_call:
    case nir_instr_type_phi:
       return 1;