pc-bios/s390-ccw: build for z900

Newer distributions have an architecture level set to z9, z196
or similar - also as default option for the compiler.

We should build the bios for z900 to allow it to run with
all 64bit CPUs. This will become more important as soon as
QEMU/KVM does support CPU models.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Acked-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-By: NSascha Silbe <silbe@linux.vnet.ibm.com>
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>

pc-bios/s390-ccw/Makefile

@@ -10,7 +10,7 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
 .PHONY : all clean build-all
 
 OBJECTS = start.o main.o bootmap.o sclp-ascii.o virtio.o
-CFLAGS += -fPIE -fno-stack-protector -ffreestanding
+CFLAGS += -fPIE -fno-stack-protector -ffreestanding -march=z900
 CFLAGS += -fno-delete-null-pointer-checks -msoft-float
 LDFLAGS += -Wl,-pie -nostdlib