NTB: ntb_transport: Free MWs in ntb_transport_link_cleanup()

NTB: ntb_transport: Free MWs in ntb_transport_link_cleanup()

If NTB peer host crashes or reboots, the NTB transport link will be
down and the MWs of NTB transport will be invalid. But the
ntb_transport_link_cleanup() does not free these invalid MWs. When
the NTB peer host is recovered later, NTB transport link will be
up and the ntb_set_mw() will not reset up MWs. Because the MWs of
NTB transport are invalid, the NTB transport will not work.

We can fix it by freeing MWs when NTB transport link is down, then
the ntb_set_mw() will reset up MWs when NTB transport link is up.

Signed-off-by: Joey Zhang <joey.zhang@microchip.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>