IB/isert: Remove unused file iser_proto.h

We don't need iser_proto.h anymore, remove it and
move (non-protocol) declarations to ib_isert.h

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Jenny Derzhavetz <jennyf@mellanox.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Doug Ledford <dledford@redhat.com>