MAINTAINERS: mark cifs mailing list as "moderated for non-subscribers"

If non-subscribers post bug report to CIFS mailing list, they will get
following messages.

	Your mail to 'linux-cifs-client' with the subject

	    [PATCH x/x] cifs: xxxxxxxxxxxxx

	Is being held until the list moderator can review it for approval.

	The reason it is being held:

	    Post by non-member to a members-only list

	Either the message will get posted to the list, or you will receive
	notification of the moderator's decision.  If you would like to cancel
	this posting, please visit the following URL:

members-only list should be written as so in MAINTAINERS file.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>