avutil/hwcontext_vdpau: Correctly initialise pixfmts

The number of declared vdpau formats can vary depending on which
version of libvdpau we build against, so the number of pix fmts
can vary too. Let's make sure we keep those numbers in sync.

libavutil/hwcontext_vdpau.c

@@ -32,27 +32,6 @@
 #include "pixfmt.h"
 #include "pixdesc.h"
 
-typedef struct VDPAUDeviceContext {
-    VdpVideoSurfaceQueryGetPutBitsYCbCrCapabilities *get_transfer_caps;
-    VdpVideoSurfaceGetBitsYCbCr                     *get_data;
-    VdpVideoSurfacePutBitsYCbCr                     *put_data;
-    VdpVideoSurfaceCreate                           *surf_create;
-    VdpVideoSurfaceDestroy                          *surf_destroy;
-
-    enum AVPixelFormat *pix_fmts[8];
-    int              nb_pix_fmts[8];
-} VDPAUDeviceContext;
-
-typedef struct VDPAUFramesContext {
-    VdpVideoSurfaceGetBitsYCbCr *get_data;
-    VdpVideoSurfacePutBitsYCbCr *put_data;
-    VdpChromaType chroma_type;
-    int chroma_idx;
-
-    const enum AVPixelFormat *pix_fmts;
-    int                       nb_pix_fmts;
-} VDPAUFramesContext;
-
 typedef struct VDPAUPixFmtMap {
     VdpYCbCrFormat vdpau_fmt;
     enum AVPixelFormat pix_fmt;
@@ -103,6 +82,27 @@ static const struct {
 #endif
 };
 
+typedef struct VDPAUDeviceContext {
+    VdpVideoSurfaceQueryGetPutBitsYCbCrCapabilities *get_transfer_caps;
+    VdpVideoSurfaceGetBitsYCbCr                     *get_data;
+    VdpVideoSurfacePutBitsYCbCr                     *put_data;
+    VdpVideoSurfaceCreate                           *surf_create;
+    VdpVideoSurfaceDestroy                          *surf_destroy;
+
+    enum AVPixelFormat *pix_fmts[FF_ARRAY_ELEMS(vdpau_pix_fmts)];
+    int              nb_pix_fmts[FF_ARRAY_ELEMS(vdpau_pix_fmts)];
+} VDPAUDeviceContext;
+
+typedef struct VDPAUFramesContext {
+    VdpVideoSurfaceGetBitsYCbCr *get_data;
+    VdpVideoSurfacePutBitsYCbCr *put_data;
+    VdpChromaType chroma_type;
+    int chroma_idx;
+
+    const enum AVPixelFormat *pix_fmts;
+    int                       nb_pix_fmts;
+} VDPAUFramesContext;
+
 static int count_pixfmts(const VDPAUPixFmtMap *map)
 {
     int count = 0;