IB/core: Avoid calling ib_query_device

Use the cached copy of the attributes present on the device, except for
the case of a query originating from user-space, where we have to invoke
the driver query_device entry, so they can fill in their udata.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>