tests/lavf-regression: fix gbrp10 dpx test on big endian

For some reason only for that pix format decoder picks native format.
Signed-off-by: Paul B Mahol <onemda@gmail.com>

tests/lavf-regression.sh

@@ -246,7 +246,7 @@ fi
 
 if [ -n "$do_dpx" ] ; then
 do_image_formats dpx
-do_image_formats dpx "-pix_fmt gbrp10le"
+do_image_formats dpx "-pix_fmt gbrp10le" "-pix_fmt gbrp10le"
 do_image_formats dpx "-pix_fmt gbrp12le"
 do_image_formats dpx "-pix_fmt rgb48le"
 do_image_formats dpx "-pix_fmt rgb48le -bits_per_raw_sample 10" "-pix_fmt rgb48le"