sndio_dec: Add missing includes for av_gettime()

This is necessary after the old av_gettime in libavformat was
dropped.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavdevice/sndio_dec.c

@@ -25,6 +25,7 @@
 #include "libavformat/avformat.h"
 #include "libavformat/internal.h"
 #include "libavutil/opt.h"
+#include "libavutil/time.h"
 
 #include "sndio_common.h"