svga: re-enable deleted surface caching

Basically, instead of immediately freeing deleted surfaces, hang onto
them in a cache to do quick re-allocation.  This helps when surfaces
are frequently destroyed and then reallocated a bit later.

Reviewed-by: José Fonseca <jfonseca@vmware.com>

src/gallium/drivers/svga/svga_resource_texture.c

@@ -433,8 +433,7 @@ svga_texture_create(struct pipe_screen *screen,
       tex->key.numFaces = 1;
    }
 
-   /* XXX: Disabled for now */
-   tex->key.cachable = 0;
+   tex->key.cachable = 1;
 
    if (template->bind & PIPE_BIND_SAMPLER_VIEW)
       tex->key.flags |= SVGA3D_SURFACE_HINT_TEXTURE;