s390x: do not include ram_addr.h

ram_addr.h is an internal interface and it is not needed anyway by
hw/s390x/ipl.c.

Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Thomas Huth <huth@tuxfamily.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1427295389-5054-1-git-send-email-pbonzini@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>