s390/con3270: fix minor checkpatch issues

Fix remaining checkpatch issues, like misplaced brackets,
whitespace and similar things. No functional change.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>