boot/efi: don't hard fail on error for tpm measure (#6473)

Display the error for a small amount of time, but don't fail hard.

In case of a faulty BIOS, a TPM error should not prevent the boot.
If something cares about the PCM measurement, it will be noticed
anyway later on.

Especially important now, that TPM measurement is the default now on
some distribution builds.

https://bugzilla.redhat.com/show_bug.cgi?id=1411156