fix(plat/xilinx/versal): resolve misra R10.3

MISRA Violation: MISRA-C:2012 R.10.3
- The value of an expression shall not be assigned to an object with a
  narrower essential type or of a different essential type category

Signed-off-by: Abhyuday Godhasara <abhyuday.godhasara@xilinx.com>
Change-Id: I9c6dd8dba40db8067b46947ceff295732648612a
diff --git a/plat/xilinx/versal/plat_versal.c b/plat/xilinx/versal/plat_versal.c
index 107eae6..15b89bf 100644
--- a/plat/xilinx/versal/plat_versal.c
+++ b/plat/xilinx/versal/plat_versal.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2018-2021, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -17,5 +17,5 @@
 		return -1;
 	}
 
-	return versal_calc_core_pos(mpidr);
+	return (int)versal_calc_core_pos(mpidr);
 }