staging: comedi: ni_at_a2150: remove A2150_DEBUG

The A2150_DEBUG define enables some development messages, specifically
the ni_dum_regs() function. These messages are just added noise. Remove
them.

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>