Currently, if bcm2835_audio_open() fails partway, the allocated
workqueue is leaked. Avoid that.

While at it, propagate the return value of
bcm2835_audio_open_connection() on failure instead of returning -1.
Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>