s390-ccw.img: Allow bigger ramdisk sizes or offsets

s390-ccw.img: Allow bigger ramdisk sizes or offsets

The s390-ccw bios creates the the virtqueue at 100MB. For
big ramdisks or offsets (via zipl) this gets overwritten.
As a quick band-aid, lets move the virtqueue into the bss
section, which is at 0x7f00000. As the bios code (text) is
at 0x7e00000 we can now handle ramdisk which are  ~27MB
bigger.

Long term we want to make the s390-ccw bios position
independent and load of at the end of memory.

Reported-by: Alexander Graf <[email protected]>
Signed-off-by: Christian Borntraeger <[email protected]>
Acked-by: Cornelia Huck <[email protected]>
Message-Id: <1425310029[email protected]>