Merge branch 'devlink-kernel-region-snapshot-id-allocation'

Jakub Kicinski says:

====================
devlink: kernel region snapshot id allocation

currently users have to find a free snapshot id to pass
to the kernel when they are requesting a snapshot to be
taken.

This set extends the kernel so it can allocate the id
on its own and send it back to user space in a response.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>