s390x: Introduce machine definition macros

s390x: Introduce machine definition macros

Most of the machine definition code looks the same between different
machine versions. The new DEFINE_CCW_MACHINE macro makes defining a
new machine easier by inserting standard machine version
definitions. This also makes it possible to propagate values between
machine versions.

The patch is inspired by code from hw/ppc/spapr.c

Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>