IB/ipath: Fix error returned from ib_resize_cq if new size smaller than # entries

The gen2_basic tests check for the errno value when a CQ is resized
smaller than the number of outstanding completions queue on the CQ.
This patch changes ib_ipath to return EINVAL which is what ib_mthca
returns and what gen2_basic expects.

Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>