ipvs: Clean up comment style in ip_vs.h

* Consistently use the multi-line comment style for networking code:

  /* This
   * That
   * The other thing
   */

* Use single-line comment style for comments with only one line of text.

* In general follow the leading '*' of each line of a comment with a
  single space and then text.

* Add missing line break between functions, remove double line break,
  align comments to previous lines whenever possible.
Reported-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>