staging: comedi: ni_labpc: remove range_labpc_1200_ai export

The 'ai_range_table' boardinfo is only used to initialize the
analog input subdevice s->range_table. We can use the 'is_labpc1200'
flag in the boardinfo to determine which range table is needed.

This allows making range_labpc_1200_ai static and removing the
export as well as removing the 'ai_range_table' from the boardinfo.

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