xprtrdma: Take struct ib_qp_attr and ib_qp_init_attr off the stack

Reduce stack footprint of the connection upcall handler function.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>