RDMA: Mark if destroy address handle is in a sleepable context

Introduce a 'flags' field to destroy address handle callback and add a
flag that marks whether the callback is executed in an atomic context or
not.

This will allow drivers to wait for completion instead of polling for it
when it is allowed.

Signed-off-by: Gal Pressman <galpress@amazon.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>