Merge tag 's390-ccw-bios-2019-05-08' into s390-next-staging

Skip unsupported bootmap signature entries instead of aborting the boot process

# gpg: Signature made Wed 08 May 2019 11:42:24 AM CEST
# gpg:                using RSA key 2ED9D774FE702DB5
# gpg: Good signature from "Thomas Huth <th.huth@gmx.de>" [full]
# gpg:                 aka "Thomas Huth <thuth@redhat.com>" [undefined]
# gpg:                 aka "Thomas Huth <huth@tuxfamily.org>" [undefined]
# gpg:                 aka "Thomas Huth <th.huth@posteo.de>" [unknown]

* tag 's390-ccw-bios-2019-05-08':
  pc-bios/s390: Update firmware image with "Skip bootmap signature entries" fix
  s390-bios: Skip bootmap signature entries
  pc-bios/s390-ccw: Clean up harmless misuse of isdigit()