cifs: remove an potentially confusing, obsolete comment

The recent commit 6ca9f3bae8b1854794dfa63cdd3b88b7dfe24c13 modified the code so
that filp is full instantiated whenever the file is created and passed back.
The below comment is no longer true, remove it.

Cc: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Steve French <sfrench@us.ibm.com>