TPM 1.2 support for Intel TXT path in GRUB

[miczyg1]

The problem you're addressing (if any)
GRUB with TrenchBoot support refuses to perform measured launch on Intel TXT enabled platform with TPM 1.2. The TPM 1.2 is reported as unsupported.

Describe the solution you'd like
Implement the TrechBoot support for TPM 1.2 for Intel TXT path in GRUB.

Where is the value to a user, and who might that user be?
Users with a slightly older platform still have TPM 1.2 onboard. The Intel ACMs are tightly coupled to TPM versions that were available at the time of platform shipment OR the TPMs are soldered and there are no means to upgrade their firmware even if the Intel ACM supports TPM2.0. Because of this, platforms owners might not be able to use TrenchBoot.

Describe alternatives you've considered
There are a few alternatives, but I do not consider them valid in my case:

• buy newer hardware with TPM 2.0
• use Intel Trusted Boot (tboot)

Additional context
When GRUB debugging is enabled for slaunch module, the GRUB prints an error on the debug console TPM 1.2 is not supported:

Relevant documentation you've consulted
https://github.com/TrenchBoot/grub/blob/intel-txt/grub-core/loader/i386/txt/txt.c#L617

Related, non-duplicate issues
None