mesa: fix a leak in _mesa_delete_texture_image()

Valgrind complains about a definitely lost block allocated in
intelNewTextureImage(). This leak was apparently created by
6e0f9001fe, "mesa: move
gl_texture_image::Data, RowStride, ImageOffsets to swrast", as it
removes the free() from _mesa_delete_texture_image().

Put the free() back, fixes a Valgrind error.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/main/teximage.c

@@ -604,6 +604,7 @@ _mesa_delete_texture_image(struct gl_context *ctx,
     */
    ASSERT(ctx->Driver.FreeTextureImageBuffer);
    ctx->Driver.FreeTextureImageBuffer( ctx, texImage );
+   free(texImage);
 }