fix(guid-partition): initialise the mbr_entry variable

The compiler complains that it may be used unitialised. Give it some
confidence that won't be the case.

Change-Id: I14bddd48e4b205121415025175f157b92a89aa26
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
diff --git a/drivers/partition/partition.c b/drivers/partition/partition.c
index c4f7493..387469c 100644
--- a/drivers/partition/partition.c
+++ b/drivers/partition/partition.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2024, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2025, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -399,7 +399,7 @@
 int load_partition_table(unsigned int image_id)
 {
 	uintptr_t dev_handle, image_handle, image_spec = 0;
-	mbr_entry_t mbr_entry;
+	mbr_entry_t mbr_entry = {0};
 	int result;
 
 	result = plat_get_image_source(image_id, &dev_handle, &image_spec);