fix(vglite) set cache invalidation callback for all handlers

This is necessary after the changes in c37ad55160
	feat(draw_buf): make draw buf API more OOP style
which indirectly changes the font drawing handlers from default_handlers to
font_draw_buf_handlers

Because the cache invalidation in vglite was enabled only for
default handlers this resulted in broken font rendering when vglite draw
unit was used.

Signed-off-by: Cristian Stoica <cristianmarian.stoica@nxp.com>

src/draw/lv_draw_buf.c

@@ -83,6 +83,16 @@ lv_draw_buf_handlers_t * lv_draw_buf_get_handlers(void)
     return &default_handlers;
 }
 
+lv_draw_buf_handlers_t * lv_draw_buf_get_font_handlers(void)
+{
+    return &font_draw_buf_handlers;
+}
+
+lv_draw_buf_handlers_t * lv_draw_buf_get_image_handlers(void)
+{
+    return &image_cache_draw_buf_handlers;
+}
+
 uint32_t lv_draw_buf_width_to_stride(uint32_t w, lv_color_format_t color_format)
 {
     return lv_draw_buf_width_to_stride_ex(&default_handlers, w, color_format);

src/draw/lv_draw_buf.h

@@ -129,6 +129,9 @@ void lv_draw_buf_handlers_init(lv_draw_buf_handlers_t * handlers,
  * @return                  pointer to the struct of handlers
  */
 lv_draw_buf_handlers_t * lv_draw_buf_get_handlers(void);
+lv_draw_buf_handlers_t * lv_draw_buf_get_font_handlers(void);
+lv_draw_buf_handlers_t * lv_draw_buf_get_image_handlers(void);
+
 
 /**
  * Align the address of a buffer. The buffer needs to be large enough for the real data after alignment

src/draw/nxp/vglite/lv_draw_buf_vglite.c

@@ -51,8 +51,12 @@ static void _invalidate_cache(const lv_draw_buf_t * draw_buf, const lv_area_t *
 void lv_draw_buf_vglite_init_handlers(void)
 {
     lv_draw_buf_handlers_t * handlers = lv_draw_buf_get_handlers();
+    lv_draw_buf_handlers_t * font_handlers = lv_draw_buf_get_font_handlers();
+    lv_draw_buf_handlers_t * image_handlers = lv_draw_buf_get_image_handlers();
 
     handlers->invalidate_cache_cb = _invalidate_cache;
+    font_handlers->invalidate_cache_cb = _invalidate_cache;
+    image_handlers->invalidate_cache_cb = _invalidate_cache;
 }
 
 /**********************