net: split out functions related to registering inflight socket files
We need this functionality for the io_uring file registration, but
we cannot rely on it since CONFIG_UNIX can be modular. Move the helpers
to a separate file, that's always builtin to the kernel if CONFIG_UNIX is
No functional changes in this patch, just moving code around.
Reviewed-by: Hannes Reinecke <firstname.lastname@example.org>
Acked-by: David S. Miller <email@example.com>
Signed-off-by: Jens Axboe <firstname.lastname@example.org>