staging: comedi: addi_common: remove addi_find_boardinfo()

All the users of the addi_common code now set the dev->board_ptr
before calling addi_auto_attach(). Remove the unnecessary function
that searches for the boardinfo.

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