CIFS: Remove some obsolete comments

Remove some obsolete comments in the cifs inode_operations
structs that were pointed out by Stephen Rothwell.

CC: Stephen Rothwell <sfr@canb.auug.org.au>
CC: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Steve French <steve.french@primarydata.com>