avfilter/vf_vpp_qsv: Fix leak of AVFilterFormats on error

avfilter/vf_vpp_qsv: Fix leak of AVFilterFormats on error

The vpp_qsv's query_formats function allocated two AVFilterFormats,
before storing them permanently. If storing the first of them fails,
the function simply returns and the second leaks. This has been fixed by
only allocating the second AVFilterFormats structure after the first one
has been successfully stored.

Fixes Coverity issue #1422231.

Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>