RDMA/iw_cxgb4: cleanup device debugfs entries on ULD remove

Remove device specific debugfs entries immediately if LLD detaches a
particular ULD device in case of fatal PCI errors.

Link: https://lore.kernel.org/r/20200524190814.17599-1-bharat@chelsio.com


Signed-off-by: Potnuri Bharat Teja <bharat@chelsio.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>