Comment 5 for bug 1830243

On top of v4.0 we only need:
2497b4a3c0 s390-bios: Skip bootmap signature entries

but can take a relatively harmless as well:
796588ba1 pc-bios/s390-ccw: Clean up harmless misuse of isdigit()

On top of 3.1 we probably want all of these:
$ git log --oneline 63c93fac18.. pc-bios/s390-ccw
2497b4a3c0 s390-bios: Skip bootmap signature entries
d796588ba1 pc-bios/s390-ccw: Clean up harmless misuse of isdigit()
2880469c95 s390-bios: Use control unit type to find bootable devices
efa47d36da s390-bios: Support booting from real dasd device
69333c36dc s390-bios: Add channel command codes/structs needed for dasd-ipl
3668cb7ce8 s390-bios: Use control unit type to determine boot method
9de6cbb152 s390-bios: Refactor virtio to run channel programs via cio
7b361db37b s390-bios: Factor finding boot device out of virtio code path
930072d2bf s390-bios: Extend find_dev() for non-virtio devices
86c58705bb s390-bios: cio error handling
3083a1bbb8 s390-bios: Support for running format-0/1 channel programs
1fb3e5cde8 s390-bios: ptr2u32 and u32toptr
c95df3d108 s390-bios: Map low core memory
120d04103e s390-bios: Decouple channel i/o logic from virtio
d96c5db77f s390-bios: Clean up cio.h
a5f6e0975b s390-bios: decouple common boot logic from virtio
87f910c142 s390-bios: decouple cio setup from virtio
0d3a761398 pc-bios/s390-ccw: Use proper register names for Clang