s390/sclp: fix .data section specification

"__section(data)" has to be "__section(.data)". __section(data)
produces extra "data" section in addition to ".data" section.

Signed-off-by: Vasily Gorbik <gor@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>