obs-ffmpeg: Set needs_compat_ver before struct version checks

Because 4a8e8bb changed the
NVENCAPI_STRUCT_VERSION define to rely on enc->needs_compat_ver, we must
do the conditional check and define needs_compat_ver before any structs
are initialized because they will check the version when doing so by
calling NVENCAPI_STRUCT_VERSION internally.

In this case, make sure that we define enc->needs_compat_ver before
NV_ENCODE_API_FUNCTION_LIST_VER is called for
NV_ENCODE_API_FUNCTION_LIST.

(cherry picked from commit 24470b3)

Author: RytoEX

plugins/obs-ffmpeg/obs-nvenc.c

@@ -1105,6 +1105,9 @@ static void *nvenc_create_internal(enum codec_type codec, obs_data_t *settings,
 	enc->codec = codec;
 	enc->first_packet = true;
 
+	if (get_nvenc_ver() == COMPATIBILITY_VERSION) {
+		enc->needs_compat_ver = true;
+	}
 	NV_ENCODE_API_FUNCTION_LIST init = {NV_ENCODE_API_FUNCTION_LIST_VER};
 
 	switch (enc->codec) {
@@ -1128,9 +1131,6 @@ static void *nvenc_create_internal(enum codec_type codec, obs_data_t *settings,
 	if (!init_d3d11(enc, settings)) {
 		goto fail;
 	}
-	if (get_nvenc_ver() == COMPATIBILITY_VERSION) {
-		enc->needs_compat_ver = true;
-	}
 	if (!init_session(enc)) {
 		goto fail;
 	}