Some additional Info and a workaround: I forgot to mention that i don't use the TPM-Chip. In fact it was disabled in the BIOS. And yes: I have tried to turn it on and off again.
Booting with the recent 4.8 Kernel i get something like that in the dmesg: tpm_tis 00:05: 1.2 TPM (device-id 0x3203, rev-id 9) tpm tpm0: tpm_transmit: tpm_send: error -5 tpm_tis 00:05: Could not get TPM timeouts and durations So i get an error message, but no oops or the like. Everything works as expected. As a workaround i booted with the option "tpm_tis.interrupts=0". No stack overflow occurs with this option on the 4.9 kernel anymore. So, if for some reason this bug can't get solved, anyone who runs in this issue should place a GRUB_CMDLINE_LINUX="tpm_tis.interrupts=0" in his/hers "/etc/default/grub", run update-grub and should be fine. Hth, niels