staging: comedi: mpc624: use tabs for whitespace instead of spaces

For aesthetics, use tabs instead of spaces for the whitespace in the
register defines.
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>