RDMA/qedr: Fix QP state initialization race

Once the FW is transitioned to error, FLUSH cqes can be received.
We want the driver to be aware of the fact that QP is already in error.

Without this fix, a user may see false error messages in the dmesg log,
mentioning that a FLUSH cqe was received while QP is not in error state.

Fixes: cecbcddf ("qedr: Add support for QP verbs")
Signed-off-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Signed-off-by: Ariel Elior <Ariel.Elior@cavium.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>