staging: comedi: pcl812: all board types have analog inputs

All the boards supported by this driver have 16 or 32 analog input
channels.

Remove the unnecessary check in pcl812_attach() to reduce the indent
level of the code.

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>