cxl: Check qos_class validity on memdev probe

Add a check to make sure the qos_class for the device will match one of
the root decoders qos_class. If no match is found, then the qos_class for
the device is set to invalid. Also add a check to ensure that the device's
host bridge matches to one of the root decoder's downstream targets.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/170319626313.2212653.9021004640856081917.stgit@djiang5-mobl3


Signed-off-by: Dan Williams <dan.j.williams@intel.com>