feat(qemu): add dummy plat_mboot_measure_key() function

Adds a dummy implementation of the plat_mboot_measure_key() function for
QEMU platform.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Change-Id: I64c1c751348c04cd359c075fc15a0d180ff55918
diff --git a/plat/qemu/qemu/qemu_measured_boot.c b/plat/qemu/qemu/qemu_measured_boot.c
index 122bb23..077f7a4 100644
--- a/plat/qemu/qemu/qemu_measured_boot.c
+++ b/plat/qemu/qemu/qemu_measured_boot.c
@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2022, Arm Limited. All rights reserved.
- * Copyright (c) 2022, Linaro.
+ * Copyright (c) 2022-2023, Linaro.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -118,3 +118,9 @@
 
 	return 0;
 }
+
+int plat_mboot_measure_key(const void *pk_oid, const void *pk_ptr,
+			   size_t pk_len)
+{
+	return 0;
+}