configure: properly add dxva2 link dependencies

Fixes building with --disable-everything --enable-shared --enable-dxva2

The hwcontext DXVA2 implementation in avutil needs this library now, instead
of just the ffmpeg program.

configure

@@ -2540,6 +2540,7 @@ crystalhd_deps="libcrystalhd_libcrystalhd_if_h"
 cuvid_deps="cuda"
 d3d11va_deps="d3d11_h dxva_h ID3D11VideoDecoder ID3D11VideoContext"
 dxva2_deps="dxva2api_h DXVA2_ConfigPictureDecode"
+dxva2_extralibs="-luser32"
 vaapi_deps="va_va_h"
 vda_framework_deps="VideoDecodeAcceleration_VDADecoder_h"
 vda_framework_extralibs="-framework VideoDecodeAcceleration"
@@ -6318,7 +6319,7 @@ if test $target_os = "haiku"; then
 fi
 
 enabled_all dxva2 dxva2api_cobj CoTaskMemFree &&
-    prepend ffmpeg_libs $($ldflags_filter "-lole32" "-luser32") &&
+    prepend ffmpeg_libs $($ldflags_filter "-lole32") &&
     enable dxva2_lib
 
 ! enabled_any memalign posix_memalign aligned_malloc &&