nir: Print divergence status of SSA values if analysis was ever run.

After running divergence analysis, we include "div" or "con" for each
SSA def's divergence/convergence status:

	vec1 32 div ssa_35 = fddy ssa_34
	vec1 32 con ssa_36 = fddy ssa_6.x

We omit this before the first time divergence analysis has been run.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15445>

src/compiler/shader_info.h

@@ -254,6 +254,9 @@ typedef struct shader_info {
     */
    bool uses_fddx_fddy:1;
 
+   /** Has divergence analysis ever been run? */
+   bool divergence_analysis_run:1;
+
    /* Bitmask of bit-sizes used with ALU instructions. */
    uint8_t bit_sizes_float;
    uint8_t bit_sizes_int;