[S390] Remove last traces of cio_msg=.

cio_msg= is gone, also remove it from kernel-parameters.txt.
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Documentation/kernel-parameters.txt

@@ -398,9 +398,6 @@ and is between 256 and 4096 characters. It is defined in the file
 	cio_ignore=	[S390]
 			See Documentation/s390/CommonIO for details.
 
-	cio_msg=	[S390]
-			See Documentation/s390/CommonIO for details.
-
 	clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
 			[Deprecated]
 			Forces specified clocksource (if available) to be used