qsvenc: restrict multi-frame encode to MFX_VERSION < 2.0

Multi-frame encode isn't supported for MFX_VERSION >= 2.0[1][2]. This is
in preparation for oneVPL support

[1] https://spec.oneapi.io/versions/latest/elements/oneVPL/source/VPL_intel_media_sdk.html#msdk-full-name-feature-removals
[2] https://github.com/oneapi-src/oneVPL

libavcodec/qsvenc.h

@@ -44,7 +44,7 @@
 #else
 #define QSV_HAVE_AVBR   0
 #define QSV_HAVE_VCM    0
-#define QSV_HAVE_MF     1
+#define QSV_HAVE_MF     !QSV_ONEVPL
 #endif
 
 #define QSV_COMMON_OPTS \