s390/disassambler: use pr_cont where appropriate

Just like for dumpstack use pr_cont instead of simple printk calls to
fix the output when disassembling a piece of code.

Before:
[    0.840627] Krnl Code: 000000000017d1c6: a77400f7            brc     7,17d3b4
[    0.840630]
                          000000000017d1ca: 92015000            mvi     0(%r5),1
[    0.840634]
                         #000000000017d1ce: a7f40001            brc     15,17d1d0

After:
[    0.831792] Krnl Code: 000000000017d13e: a77400f7            brc     7,17d32c
                          000000000017d142: 92015000            mvi     0(%r5),1
                         #000000000017d146: a7f40001            brc     15,17d148

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>