tpm: Add TPM2 support for write_lock

Implement this API function for TPM2.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/lib/tpm_api.c b/lib/tpm_api.c
index 687fc8b..4c66264 100644
--- a/lib/tpm_api.c
+++ b/lib/tpm_api.c
@@ -144,7 +144,7 @@
 	if (is_tpm1(dev))
 		return -ENOSYS;
 	else if (is_tpm2(dev))
-		return -ENOSYS;
+		return tpm2_write_lock(dev, index);
 	else
 		return -ENOSYS;
 }