fundamental: rename tpm-pcr.h → tpm2-pcr.h

fundamental: rename tpm-pcr.h → tpm2-pcr.h

I always found it confusing that most of our TPM related definitions are
in tpm2-util.h, but the PCR names in tpm-pcr.h, without the "2". Let's
fix that and make this systematic, in particular as the definitions in
the file all start with TPM2_ already.

No code flow changes, just some renaming.