avcodec/vdpau: Initialise driver version variable explicitly

If the identification string ever changed, we might not match anything
in the sscanf(). At least have predictable behaviour.

libavcodec/vdpau.c

@@ -208,7 +208,7 @@ int ff_vdpau_common_init(AVCodecContext *avctx, VdpDecoderProfile profile,
         return vdpau_error(status);
     if (avctx->codec_id == AV_CODEC_ID_HEVC && strncmp(info_string, "NVIDIA ", 7) == 0 &&
         !(avctx->hwaccel_flags & AV_HWACCEL_FLAG_ALLOW_PROFILE_MISMATCH)) {
-        int driver_version;
+        int driver_version = 0;
         sscanf(info_string, "NVIDIA VDPAU Driver Shared Library  %d", &driver_version);
         if (driver_version < 410) {
             av_log(avctx, AV_LOG_VERBOSE, "HEVC with NVIDIA VDPAU drivers is buggy, skipping.\n");