Place attribute_deprecated in the right position for struct declarations

libavcodec/vaapi.h:58:1: warning: attribute 'deprecated' is ignored, place it after "struct" to apply attribute to type declaration [-Wignored-attributes]

(cherry picked from commit ed6a891c)
Signed-off-by: Mark Thompson <sw@jkqxz.net>

libavcodec/vaapi.h

@@ -53,8 +53,7 @@
  *
  * Deprecated: use AVCodecContext.hw_frames_ctx instead.
  */
-attribute_deprecated
-struct vaapi_context {
+struct attribute_deprecated vaapi_context {
     /**
      * Window system dependent data
      *