s390/tools: generate header files in arch/s390/include/generated/

Previously, the generated dis.h and facilities.h header files have been
stored in include/generated.  Because they are s390 specific, store them
in the arch/s390/include/generated/asm/ directory.  Also update
references to the header files respectively.

To prevent name collisions with those header files in asm/ that
include the generated ones, rename the generated headers files
and add an -defs suffix.  Also update the generators to create
the ifdef guards respectively.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>