IB/mthca: Don't read reserved fields in mthca_QUERY_ADAPTER()

For memfree devices, the firmware QUERY_ADAPTER command does not
return vendor_id, device_id, and revision_id; do not return these
fields in the QUERY_ADAPTER function for memfree devices.

Instead, for memfree devices, initialize the rev_id field of the mthca
device via init_node_data (MAD IFC query), as is done in the
query_device verb implementation.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>