Staging: comedi: jr3_pci: Don't ioremap too much space. Check result.

For the JR3/PCI cards, the size of the PCIBAR0 region depends on the
number of channels.  Don't try and ioremap space for 4 channels if the
card has fewer channels.  Also check for ioremap failure.

Thanks to Anders Blomdell for input and Sami Hussein for testing.

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