lavc/qsv: fix make checkheaders warning

make checkheaders will get warning as follow:

In file included from libavcodec/qsv_internal.h.c:1:
./libavcodec/qsv_internal.h:24:5: warning: "CONFIG_VAAPI" is not defined, evaluates to 0 [-Wundef]
   24 | #if CONFIG_VAAPI
      |     ^~~~~~~~~~~~

include "config.h" to fix the warning

Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

libavcodec/qsv_internal.h

@@ -21,6 +21,8 @@
 #ifndef AVCODEC_QSV_INTERNAL_H
 #define AVCODEC_QSV_INTERNAL_H
 
+#include "config.h"
+
 #if CONFIG_VAAPI
 #define AVCODEC_QSV_LINUX_SESSION_HANDLE
 #endif //CONFIG_VAAPI