pc-bios/s390-ccw: avoid floating point operations

Some gcc versions (e.g. Fedora 22 gcc 5.1.1) seem to use floating
point registers for spilling and filling of general purpose registers.
As the BIOS does not activate the AFP register setting of CR0 this can
cause data exception program checks.
Disallow floating point in the BIOS as a simple solution.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Message-Id: <1443689387-34473-2-git-send-email-jfrei@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
