[PATCH] IB/mthca: Use correct port width capability value

When we call the INIT_IB firmware command to bring up a port, use
the actual port width capability returned by the QUERY_DEV_LIM
command instead of always trying to enable both 1X and 4X.  This
fixes breakage seen when the firmware is build to allow 4X only.

Signed-off-by: Roland Dreier <rolandd@cisco.com>