xhci: fix incorrect type in assignment in xhci_address_device()

The field 'dev_info' in struct xhci_slot_ctx has type __le32 and it needs
to be converted to CPU byteorder for the correct retrieval of its subfield
'Context Entries'. This field is used by the trace event 'xhci_address_ctx'
to trace only the contexts of valid endpoints.
This bug was found using sparse.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>