This kind of reverts 7b596416bf ("Gigabeat S: Update RDS processing to
use asynchronous I2C rather than thread."). However, requiring RDS to
run in thread context will a) allow more upcoming features and b) remove
quite some complexity from the codebase (see the diffstat here) because
Gigabeat is the only user. iMX31 should be able to handle one more
thread, as it can even run Linux.
Change-Id: I46130034595ba66392c5417c275d036f4bd26943