sandbox: tpm: Support nvdata in TPM2

Add support for this feature in the TPM2 emulator, to support Chromium OS
vboot.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/tpm-v2.h b/include/tpm-v2.h
index 247b386..949a13c 100644
--- a/include/tpm-v2.h
+++ b/include/tpm-v2.h
@@ -32,6 +32,8 @@
 #define TPM2_MAX_TPM_PROPERTIES ((TPM2_MAX_CAP_BUFFER - sizeof(u32) /* TPM2_CAP */ - \
 				 sizeof(u32)) / sizeof(struct tpms_tagged_property))
 
+#define TPM2_HDR_LEN		10
+
 /*
  *  We deviate from this draft of the specification by increasing the value of
  *  TPM2_NUM_PCR_BANKS from 3 to 16 to ensure compatibility with TPM2