mesa: consolidate definitions of max texture image units

Shaders are unified on most hardware (= same limits in all stages).

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/state_tracker/st_extensions.c

@@ -98,7 +98,7 @@ void st_init_limits(struct st_context *st)
    c->MaxVertexTextureImageUnits
       = _min(screen->get_shader_param(screen, PIPE_SHADER_VERTEX,
                                       PIPE_SHADER_CAP_MAX_TEXTURE_SAMPLERS),
-             MAX_VERTEX_TEXTURE_IMAGE_UNITS);
+             MAX_TEXTURE_IMAGE_UNITS);
 
    c->MaxCombinedTextureImageUnits
       = _min(screen->get_param(screen, PIPE_CAP_MAX_COMBINED_SAMPLERS),