s390/sclp: avoid merged message output

The sclp console and tty code currently uses several message text
objects in a single message event to print several lines with one
SCCB. This causes the output of these lines to be fused into a
block which is noticeable when selecting text in the operating system
message panel.

Instead use several message events with a single message text object
each to print every line on its own. This changes the SCCB layout
from

    struct sccb_header
        struct evbuf_header
            struct mdb_header
                struct go
                struct mto
		...
		struct mto

to

    struct sccb_header
        struct evbuf_header
            struct mdb_header
                struct go
                struct mto
	...
        struct evbuf_header
            struct mdb_header
                struct go
                struct mto

Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>