powerpc/rtas: Make timestamp related code y2038-safe

While we are here, let us make timestamp related code y2038-safe.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hari Bathini <hbathini@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
index d1bd001..c3c99eb 100644
--- a/arch/powerpc/include/asm/rtas.h
+++ b/arch/powerpc/include/asm/rtas.h
@@ -4,6 +4,7 @@
 
 #include <linux/spinlock.h>
 #include <asm/page.h>
+#include <linux/time.h>
 
 /*
  * Definitions for talking to the RTAS on CHRP machines.
@@ -343,7 +344,7 @@
 extern void pSeries_log_error(char *buf, unsigned int err_type, int fatal);
 
 #ifdef CONFIG_PPC_PSERIES
-extern unsigned long last_rtas_event;
+extern time64_t last_rtas_event;
 extern int clobbering_unread_rtas_event(void);
 extern int pseries_devicetree_update(s32 scope);
 extern void post_mobility_fixup(void);