Staging: comedi: convert while loop to timeout in ni_mio_common.c

This patch for ni_mio_common.c changes out a while loop for a timeout,
which is preferred.

Signed-off-by: Chase Southwood <chase.southwood@yahoo.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>