qsv: Initialize impl_value

Fixes: The warnings from CID1598553 Uninitialized scalar variable

Passing partly initialized structs is ugly and asking for hard to rieproduce bugs,
The uninitialized fields where not used

Reviewed-by: "Xiang, Haihao" <haihao.xiang-at-intel.com@ffmpeg.org>
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit c841cb45e8)

libavcodec/qsv.c

@@ -496,7 +496,7 @@ static int qsv_new_mfx_loader(AVCodecContext *avctx,
     mfxStatus sts;
     mfxLoader loader = NULL;
     mfxConfig cfg;
-    mfxVariant impl_value;
+    mfxVariant impl_value = {0};
 
     loader = MFXLoad();
     if (!loader) {

libavutil/hwcontext_qsv.c

@@ -674,7 +674,7 @@ static int qsv_d3d11_update_config(void *ctx, mfxHDL handle, mfxConfig cfg)
     IDXGIDevice *pDXGIDevice = NULL;
     HRESULT hr;
     ID3D11Device *device = handle;
-    mfxVariant impl_value;
+    mfxVariant impl_value = {0};
 
     hr = ID3D11Device_QueryInterface(device, &IID_IDXGIDevice, (void**)&pDXGIDevice);
     if (SUCCEEDED(hr)) {
@@ -748,7 +748,7 @@ static int qsv_d3d9_update_config(void *ctx, mfxHDL handle, mfxConfig cfg)
     LUID luid;
     D3DDEVICE_CREATION_PARAMETERS params;
     HRESULT hr;
-    mfxVariant impl_value;
+    mfxVariant impl_value = {0};
 
     hr = IDirect3DDeviceManager9_OpenDeviceHandle(devmgr, &device_handle);
     if (FAILED(hr)) {
@@ -830,7 +830,7 @@ static int qsv_va_update_config(void *ctx, mfxHDL handle, mfxConfig cfg)
     VADisplayAttribute attr = {
         .type = VADisplayPCIID,
     };
-    mfxVariant impl_value;
+    mfxVariant impl_value = {0};
 
     vas = vaGetDisplayAttributes(dpy, &attr, 1);
     if (vas == VA_STATUS_SUCCESS && attr.flags != VA_DISPLAY_ATTRIB_NOT_SUPPORTED) {
@@ -871,7 +871,7 @@ static int qsv_new_mfx_loader(void *ctx,
     mfxStatus sts;
     mfxLoader loader = NULL;
     mfxConfig cfg;
-    mfxVariant impl_value;
+    mfxVariant impl_value = {0};
 
     *ploader = NULL;
     loader = MFXLoad();