tpm2: downgrade most log functions from error to debug

Because most TPM2 functions here are 'library-like' functions, they should be
at debug level, not error level.

The only functions not reduced to logging at debug are tpm2_list_devices(),
since it is expected to print output, and the tpm2_parse_pcr_argument_*()
functions, since the system-wide parse_*_argument() functions generally log at
error level.

src/boot/measure.c

@@ -835,7 +835,7 @@ static int verb_sign(int argc, char *argv[], void *userdata) {
 
                         r = tpm2_calculate_policy_pcr(&pcr_value, 1, &pcr_policy_digest);
                         if (r < 0)
-                                return r;
+                                return log_error_errno(r, "Could not calculate PolicyPCR digest: %m");
 
                         _cleanup_free_ void *sig = NULL;
                         size_t ss;