staging: comedi: jr3_pci: check PCI BAR 0 size

The various supported boards have different numbers of subdevices from 1
to 4.  Each subdevice needs a block of registers in PCI BAR 0.  Check
the region is large enough for the required number of subdevices.
Return an error from `jr3_pci_auto_attach()` if it is too small.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>