VAAPI: Change some loglevels - we are spamming too much

By default we log a whole lot of things on NOTICE level, but whenever a problem arrises we ask the user for a debuglog anyways. So this PR moves debug information (e.g. starting of threads and so on) to LOGDEBUG.

Perhaps we should also adapt to the component logging - to not spam other devs when they debug something non VAAPI related.
I always thought of LOGNOTICE as something that tells you something about the environment on which XBMC is running, and consider thread creating/destruction something that belongs in LOGDEBUG.