intel: agilex: Fix build error

"result of '1 << 31' requires 33 bits to represent, but 'int' only has
32 bits [-Werror=shift-overflow=]"

This is treated as an error since commit 93c690eb

 ("Enable
-Wshift-overflow=2 to check for undefined shift behavior")

Change-Id: I141827a6711ab7759bfd6357e4ed9c1176da7c7b
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>

plat/intel/soc/agilex/include/agilex_mailbox.h

@@ -7,6 +7,8 @@
 #ifndef AGX_MBOX_H
 #define AGX_MBOX_H
 
+#include <lib/utils_def.h>
+
 #define MBOX_OFFSET			0xffa30000
 
 #define MBOX_ATF_CLIENT_ID		0x1
@@ -76,7 +78,7 @@
 #define RECONFIG_STATUS_STATE		0
 #define RECONFIG_STATUS_PIN_STATUS	2
 #define RECONFIG_STATUS_SOFTFUNC_STATUS 3
-#define PIN_STATUS_NSTATUS		(1 << 31)
+#define PIN_STATUS_NSTATUS		(U(1) << 31)
 #define SOFTFUNC_STATUS_SEU_ERROR	(1 << 3)
 #define SOFTFUNC_STATUS_INIT_DONE	(1 << 1)
 #define SOFTFUNC_STATUS_CONF_DONE	(1 << 0)