RDMA/qedr: Fix iWARP active mtu display

Currently iWARP does not support mtu-change. Notify user when MTU changes
that reload of qedr is required for mtu to change.  Display the correct
active mtu.

Fixes: f5b1b177 ("RDMA/qedr: Add iWARP support in existing verbs")
Link: https://lore.kernel.org/r/20200902165741.8355-7-michal.kalderon@marvell.com


Signed-off-by: Michal Kalderon <michal.kalderon@marvell.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>