cxl/pci: Ignore unknown register block types

In an effort to explicit avoid supporting vendor specific register
blocks (which can happily be mapped from userspace), entirely skip
probing unknown types. The secondary benefit of this will be revealed
in the future with code simplification.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20210716231548.174778-2-ben.widawsky@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>