s390/dis: move common definitions to a header file

The patch moves some of the definitions to a
header file. No functional changes involved.

I have retained the Copyright Statement from the
original file.

Signed-off-by: Suzuki K Poulose <suzuki@in.ibm.com>
[Heiko Carstens: rename s390-dis.h to dis.h]
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>