Avoid unintended "Unexpected decoder output format" messages.

They would appear for hardware acceleration formats when probing
if they are supported.
The message was only intended to be shown when the format we
select in the end is missing from codecs.conf.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@37324 b3059339-0415-0410-9bf9-f77b7e298cf2