IB/ipath: Don't initialize port memory for subports

A recent change was made to allocate memory for a port after CPU
affinity is set. That change didn't account for subports and was
trying to allocate memory for the port twice.

Signed-off-by: Bryan O'Sullivan <bryan.osullivan@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>