tpm: Pass unknown error as non-fatal, but debug print the error we got

Signed-off-by: Mathieu Trudel-Lapierre <mathieu.trudel-lapierre@canonical.com>

Bug-Debian: https://bugs.debian.org/940911
Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1848892
Last-Update: 2021-09-24

Patch-Name: tpm-unknown-error-non-fatal.patch