s390x/helper: Added format control bit to MMU translation

s390x/helper: Added format control bit to MMU translation

With the EDAT-1 facility, the MMU translation can stop at the
segment table already, pointing to a 1 MB block. And while we're
at it, move the page table entry handling to a separate function,
too, as suggested by Alexander Graf.

Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
(cherry picked from commit c4400206d43b6a235299c7047cca0af93269fc03)

Conflicts:
	target-s390x/helper.c

*removed unecessary context

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>