Eevee: SSR Clamp color when blurring buffers.

This effectivly reduce firefly bleeding all over the place.
We still need the clamp in the resolve pass because the level 0 has not been clamped.
NOTE: I did not clamped each sample individually for performance BUT I did not profile it to know how much it cost.

source/blender/draw/engines/eevee/eevee_effects.c

@@ -815,6 +815,7 @@ void EEVEE_effects_cache_init(EEVEE_SceneLayerData *sldata, EEVEE_Data *vedata)
 		psl->color_downsample_ps = DRW_pass_create("Downsample", DRW_STATE_WRITE_COLOR);
 		DRWShadingGroup *grp = DRW_shgroup_create(e_data.downsample_sh, psl->color_downsample_ps);
 		DRW_shgroup_uniform_buffer(grp, "source", &e_data.color_src);
+		DRW_shgroup_uniform_float(grp, "fireflyFactor", &effects->ssr_firefly_fac, 1);
 		DRW_shgroup_call_add(grp, quad, NULL);
 	}