staging: bcm2835-camera: handle wait_for_completion_timeout return properly

wait_for_completion_timeout returns unsigned long not int so a variable of
proper type is introduced. Further the check for <= 0 is ambiguous and
should be == 0 here indicating timeout.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Fixes: 7b3ad5ab ("staging: Import the BCM2835 MMAL-based V4L2 camera driver.")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>