pc-bios/s390: rebuild s390-ccw.img

rebuild after the following commits

4b996d0 pc-bios/s390-ccw: Link libnet into the netboot image and do the TFTP load
e6879a6 pc-bios/s390-ccw: Add virtio-net driver code
766500f pc-bios/s390-ccw: Add core files for the network bootloading program
f807e55 pc-bios/s390-ccw: Add code for virtio feature negotiation
b4e3b4f pc-bios/s390-ccw: Remove unused structs from virtio.h
dd3dc5e pc-bios/s390-ccw: Move byteswap functions to a separate header
a20b4fe pc-bios/s390-ccw: Add a write() function for stdio
262e07c pc-bios/s390-ccw: Move virtio-block related functions into a separate file
7438d32 pc-bios/s390-ccw: Move ebc2asc to sclp.c
8760bad pc-bios/s390-ccw: Move libc functions to separate header
c68f450 pc-bios/s390-ccw: use STRIP variable in Makefile

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>