staging: comedi: mpc624: remove unnecessary printk noise

The ai read timeout will return -ETIMEDOUT. The printk is just added
noise. Remove it.

It's also not necessary to set data[n[ = 0 when the read timesout.
Remove that also.

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