fate: fix sub2video_{basic, time_limited} on big-endian targets

The reference file uses BGRA pixel format, so request it here.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

tests/fate/ffmpeg.mak

@@ -62,6 +62,7 @@ fate-sub2video: CMD = framecrc -auto_conversion_filters \
 FATE_SAMPLES_FFMPEG-$(call FRAMECRC, VOBSUB, DVDSUB, SCALE_FILTER) += fate-sub2video_basic
 fate-sub2video_basic: CMD = framecrc -auto_conversion_filters \
   -i $(TARGET_SAMPLES)/sub/vobsub.idx \
+  -pix_fmt bgra \
   -fps_mode passthrough -copyts \
   -filter_complex "sws_flags=+accurate_rnd+bitexact\;[0:s:0]scale" \
   -c:v rawvideo -threads 1
@@ -71,6 +72,7 @@ fate-sub2video_basic: CMD = framecrc -auto_conversion_filters \
 FATE_SAMPLES_FFMPEG-$(call FRAMECRC, SUP, PGSSUB, SCALE_FILTER RAWVIDEO_ENCODER) += fate-sub2video_time_limited
 fate-sub2video_time_limited: CMD = framecrc -auto_conversion_filters \
   -i $(TARGET_SAMPLES)/sub/pgs_sub.sup \
+  -pix_fmt bgra \
   -fps_mode passthrough -copyts \
   -t 15 \
   -filter_complex "sws_flags=+accurate_rnd+bitexact\;[0:s:0]scale" \