RDMA/qedr: restructure functions that create/destroy QPs

Simplify function and sub-function flow of QP creation and destruction.
This also serves as a preparation for SRQ and iWARP support.

Signed-off-by: Ram Amrani <Ram.Amrani@cavium.com>
Reviewed-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>