drm/nouveau: improve handling of 64-bit BARs

GPUs exist now with a 64-bit BAR0, which mean that BAR1 and BAR2's
indices (as passed to pci_resource_len() etc) are bumped up by one.

Modify nvkm_device.resource_addr/size() to take an enum instead of
an integer bar index, and take IORESOURCE_MEM_64 into account when
translating to the "raw" bar id.

[airlied: fixup ERR_PTR]
Signed-off-by: Ben Skeggs <bskeggs@nvidia.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Timur Tabi <ttabi@nvidia.com>
Tested-by: Timur Tabi <ttabi@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>