video: driver: request api fixes for v4l2-compliance

- add support for prepare_buf
- check if client has configured invalid fd for metadata
  buffer fd control.

Change-Id: I576d02be05e4692a5ab45286895c34284f08651c
Signed-off-by: Darshana Patil <darshana@quicinc.com>

driver/vidc/inc/msm_vidc.h

@@ -28,6 +28,8 @@ int msm_vidc_g_param(void *instance, struct v4l2_streamparm *sp);
 int msm_vidc_reqbufs(void *instance, struct v4l2_requestbuffers *b);
 int msm_vidc_querybuf(void *instance, struct v4l2_buffer *b);
 int msm_vidc_create_bufs(void *instance, struct v4l2_create_buffers *b);
+int msm_vidc_prepare_buf(void *instance, struct media_device *mdev,
+	struct v4l2_buffer *b);
 int msm_vidc_release_buffer(void *instance, int buffer_type,
 		unsigned int buffer_index);
 int msm_vidc_qbuf(void *instance, struct media_device *mdev,