devlink: trivial: fix tab in function documentation

The function documentation comment for devlink_region_snapshot_create
included a literal tab character between 'future analyses' that was
difficult to spot as it happened to only display as one space wide.

Fix the comment to use a space here instead of a stray tab appearing in
the middle of a sentence.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>