tpm2/tlcl_send_startup: should pass on TPM_E_INVALID_POSTINIT

Change TSS layer tlcl_send_startup() to expose TPM_RC_INITIALIZE,
which gets mapped to TPM_E_INVALID_POSTINIT.  The return value
is exposed to TSPI layer tpm_setup(), and dealt with as follows:

- Regular startup: TPM_E_INVALID_POSTINIT should count as failure.
- S3 resume: TPM_E_INVALID_POSTINIT can be assumed to mean that
  TPM maintains power during S3, and is already initialized.

Also, correct an error where |response| could be erroneously accessed
when it is set to NULL.

BUG=b:114018226
TEST=compile coreboot

Change-Id: Ib0c3750386ae04279401c1dc318c5019d39f5ecf
Signed-off-by: Joel Kitching <kitching@google.com>
Reviewed-on: https://review.coreboot.org/29063
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

src/security/tpm/tss/tcg-2.0/tss.c

@@ -61,12 +61,24 @@ static uint32_t tlcl_send_startup(TPM_SU type)
 	startup.startup_type = type;
 	response = tpm_process_command(TPM2_Startup, &startup);
 
-	if (response && (response->hdr.tpm_code == 0 ||
+	/* IO error, tpm2_response pointer is empty. */
-			 response->hdr.tpm_code == TPM_RC_INITIALIZE)) {
+	if (response == NULL) {
-		return TPM_SUCCESS;
+		printk(BIOS_ERR, "%s: TPM communication error\n", __func__);
+		return TPM_E_IOERROR;
 	}
+
 	printk(BIOS_INFO, "%s: Startup return code is %x\n",
 	       __func__, response->hdr.tpm_code);
+
+	switch (response->hdr.tpm_code) {
+	case TPM_RC_INITIALIZE:
+		/* TPM already initialized. */
+		return TPM_E_INVALID_POSTINIT;
+	case TPM2_RC_SUCCESS:
+		return TPM_SUCCESS;
+	}
+
+	/* Collapse any other errors into TPM_E_IOERROR. */
 	return TPM_E_IOERROR;
 }