IB/ehca: Update qp_state on cached modify_qp()

Since the introduction of the port auto-detect mode for ehca, calls to
modify_qp() may be cached in the device driver when the ports are not
activated yet. When a modify_qp() call is cached, the qp state remains
untouched until the port is activated, which will leave the qp in the
reset state. In the reset state, however, it is not allowed to post SQ
WQEs, which confuses applications like ib_mad.

The solution for this problem is to immediately set the qp state as
requested by modify_qp(), even when the call is cached.

Signed-off-by: Alexander Schmidt <alexs@linux.vnet.ibm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>