Sanyo lv24020lp FM: Improve frequency measurement on PP thus improving initial frequ...

Sanyo lv24020lp FM: Improve frequency measurement on PP thus improving  initial frequency setting. Properly account for IF when tuning FM oscillator (this worked poorly before but appears to work as expected now -- aka. works for me). Not sure what this will do to iAudio7 or Cowon D2 but if they can implement a good duration measurement, they should do so or use the internal timer if possible.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27042 a1c6a512-1295-4272-9138-f99709370657