feat(versal): resolve the misra 10.1 warnings

MISRA Violation: MISRA-C:2012 R.10.1
-The operand to the operator does not have an essentially unsigned type.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@xilinx.com>
Change-Id: I9cde2f1ebceaad8a41c69489ef1d2e6f21f04ed1
diff --git a/plat/xilinx/versal/include/platform_def.h b/plat/xilinx/versal/include/platform_def.h
index 83e5083..6d95fdc 100644
--- a/plat/xilinx/versal/include/platform_def.h
+++ b/plat/xilinx/versal/include/platform_def.h
@@ -15,7 +15,7 @@
  ******************************************************************************/
 
 /* Size of cacheable stacks */
-#define PLATFORM_STACK_SIZE	0x440
+#define PLATFORM_STACK_SIZE	U(0x440)
 
 #define PLATFORM_CORE_COUNT		U(2)
 #define PLAT_MAX_PWR_LVL		U(1)