gallium: remove the pipe_sampler_state::shadow_ambient field

This was only present for the sake of GL_ARB_shadow_ambient which we
never implemented in Gallium.  If we someday want GL_ARB_shadow_ambient
we can implement it in the state tracker by adding a MAD after the
relevant TEX instructions.

src/gallium/drivers/trace/tr_dump_state.c

@@ -430,7 +430,6 @@ void trace_dump_sampler_state(const struct pipe_sampler_state *state)
    trace_dump_member(uint, state, compare_func);
    trace_dump_member(bool, state, normalized_coords);
    trace_dump_member(uint, state, prefilter);
-   trace_dump_member(float, state, shadow_ambient);
    trace_dump_member(float, state, lod_bias);
    trace_dump_member(float, state, min_lod);
    trace_dump_member(float, state, max_lod);

src/gallium/include/pipe/p_state.h

@@ -265,7 +265,6 @@ struct pipe_sampler_state
    unsigned compare_func:3;      /**< PIPE_FUNC_x */
    unsigned normalized_coords:1; /**< Are coords normalized to [0,1]? */
    unsigned prefilter:4;         /**< Wierd sampling state exposed by some api's */
-   float shadow_ambient;         /**< shadow test fail color/intensity */
    float lod_bias;               /**< LOD/lambda bias */
    float min_lod, max_lod;       /**< LOD clamp range, after bias */
    float border_color[4];

src/gallium/state_trackers/g3dvl/vl_basic_csc.c

@@ -669,7 +669,6 @@ static int vlInit
 	sampler.compare_func = PIPE_FUNC_ALWAYS;
 	sampler.normalized_coords = 1;
 	/*sampler.prefilter = ;*/
-	/*sampler.shadow_ambient = ;*/
 	/*sampler.lod_bias = ;*/
 	/*sampler.min_lod = ;*/
 	/*sampler.max_lod = ;*/

src/gallium/state_trackers/g3dvl/vl_r16snorm_mc_buf.c

@@ -1074,7 +1074,6 @@ static int vlInit
 		sampler.compare_func = PIPE_FUNC_ALWAYS;
 		sampler.normalized_coords = 1;
 		/*sampler.prefilter = ;*/
-		/*sampler.shadow_ambient = ;*/
 		/*sampler.lod_bias = ;*/
 		sampler.min_lod = 0;
 		/*sampler.max_lod = ;*/