gl_hwdec: use a imgfmt field instead of a query_format callback

Now that vdpau always uses a single image format, this can be
simplified.

video/out/gl_common.h

@@ -182,8 +182,8 @@ struct gl_hwdec {
 struct gl_hwdec_driver {
     // Same name as used by mp_hwdec_info->load_api()
     const char *api_name;
-    // Test whether the given IMGFMT_ is supported.
-    bool (*query_format)(int imgfmt);
+    // The hardware surface IMGFMT_ that must be passed to map_image later.
+    int imgfmt;
     // Create the hwdec device. It must fill in hw->info, if applicable.
     // This also must set hw->converted_imgfmt.
     int (*create)(struct gl_hwdec *hw);

video/out/gl_hwdec_vaglx.c

@@ -35,11 +35,6 @@ struct priv {
     void *vaglx_surface;
 };
 
-static bool query_format(int imgfmt)
-{
-    return imgfmt == IMGFMT_VAAPI;
-}
-
 static void destroy_texture(struct gl_hwdec *hw)
 {
     struct priv *p = hw->priv;
@@ -131,7 +126,7 @@ static void unmap_image(struct gl_hwdec *hw)
 
 const struct gl_hwdec_driver gl_hwdec_vaglx = {
     .api_name = "vaapi",
-    .query_format = query_format,
+    .imgfmt = IMGFMT_VAAPI,
     .create = create,
     .reinit = reinit,
     .map_image = map_image,

video/out/gl_hwdec_vdpau.c

@@ -40,11 +40,6 @@ struct priv {
     VdpVideoMixer video_mixer;
 };
 
-static bool query_format(int imgfmt)
-{
-    return imgfmt == IMGFMT_VDPAU;
-}
-
 static void mark_vdpau_objects_uninitialized(struct gl_hwdec *hw)
 {
     struct priv *p = hw->priv;
@@ -253,7 +248,7 @@ static void unmap_image(struct gl_hwdec *hw)
 
 const struct gl_hwdec_driver gl_hwdec_vdpau = {
     .api_name = "vdpau",
-    .query_format = query_format,
+    .imgfmt = IMGFMT_VDPAU,
     .create = create,
     .reinit = reinit,
     .map_image = map_image,

video/out/gl_video.c

@@ -1948,7 +1948,7 @@ static bool init_format(int fmt, struct gl_video *init)
         init = &dummy;
 
     init->hwdec_active = false;
-    if (init->hwdec && init->hwdec->driver->query_format(fmt)) {
+    if (init->hwdec && init->hwdec->driver->imgfmt == fmt) {
         fmt = init->hwdec->converted_imgfmt;
         init->hwdec_active = true;
     }