staging: comedi: ni_labpc: return bool from labpc_use_continuous_mode()

This is a simple true/false test, return bool instead of int.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>