tss2: Add TPM2_PCR_Event command

The TPM2_PCR_Event command is introduced to tss2 to allow the user to
extend a specific PCR. The related data structure and unmarshal function
are also introduced.

However, simply invoking TPM2_PCR_Event does not automatically record
the event into the TPM event log. The TPM event log is primarily
maintained by the system firmware (e.g., BIOS/UEFI). Therefore, for most
standard use cases, the recommended method for extending PCRs and
ensuring proper event logging is to utilize the system firmware
functions.

There are specific scenarios where direct use of TPM2_PCR_Event becomes
necessary. For instance, in environments lacking system firmware support
for PCR extension, such as the grub-emu, TPM2_PCR_Event serves as the
only available method to extend PCRs.

Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/lib/tss2/tpm2_cmd.h

@@ -89,6 +89,13 @@ grub_tpm2_unseal (const TPMI_DH_OBJECT_t item_handle,
 extern TPM_RC_t
 grub_tpm2_flushcontext (const TPMI_DH_CONTEXT_t handle);
 
+extern TPM_RC_t
+grub_tpm2_pcr_event (const TPMI_DH_PCR_t pcrHandle,
+		     const TPMS_AUTH_COMMAND_t *authCommand,
+		     const TPM2B_EVENT_t *eventData,
+		     TPML_DIGEST_VALUES_t *digests,
+		     TPMS_AUTH_RESPONSE_t *authResponse);
+
 extern TPM_RC_t
 grub_tpm2_pcr_read (const TPMS_AUTH_COMMAND_t *authCommand,
 		    const TPML_PCR_SELECTION_t *pcrSelectionIn,