mlx4_core: Save/restore default port IB capability mask

Commit 7ff93f8b

 ("mlx4_core: Multiple port type support") introduced
support for different port types.  As part of that support, SET_PORT
is invoked to set the port type during driver startup.  However, as a
side-effect, for IB ports the invocation of this command also sets the
port's capability mask to zero (losing the default value set by FW).

To fix this, get the default ib port capabilities (via a MAD_IFC Port
Info query) during driver startup, and save them for use in the
mlx4_SET_PORT command when setting the port-type to Infiniband.

This patch fixes problems with subnet manager (SM) failover such as
<https://bugs.openfabrics.org/show_bug.cgi?id=1183>, which occurred
because the IsTrapSupported bit in the capability mask was zeroed.

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