evas-software-generic: Check for render engine function before calling

In most engines which inherit from software_generic, they do not
implement the outbuf_free_region_for_update function. Most engines
have it as an unused function. If we simply add a check here, then we
can reduce the need for having useless function in multiple engines.

@fix
Signed-off-by: Chris Michael <cp.michael@samsung.com>

src/modules/evas/engines/software_generic/evas_engine.c

@@ -4289,7 +4289,8 @@ eng_output_redraws_next_update_push(void *engine EINA_UNUSED, void *data, void *
    evas_common_pipe_map_begin(surface);
 #endif /* BUILD_PIPE_RENDER */
    re->outbuf_push_updated_region(re->ob, surface, x, y, w, h);
-   re->outbuf_free_region_for_update(re->ob, surface);
+   if (re->outbuf_free_region_for_update)
+     re->outbuf_free_region_for_update(re->ob, surface);
    evas_common_cpu_end_opt();
 }