powerpc: use time64_t in update_persistent_clock

update_persistent_clock() is deprecated because it suffers from overflow
in 2038 on 32-bit architectures. This changes powerpc to use the
update_persistent_clock64() replacement, and to pass down 64-bit
timestamps consistently.

This is now simpler, as we no longer have to worry about the offset
numbers in tm_year and tm_mon that are different between the Linux
conventions and RTAS.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/8xx/m8xx_setup.c

@@ -169,15 +169,14 @@ int mpc8xx_set_rtc_time(struct rtc_time *tm)
 {
 	sitk8xx_t __iomem *sys_tmr1;
 	sit8xx_t __iomem *sys_tmr2;
-	int time;
+	time64_t time;
 
 	sys_tmr1 = immr_map(im_sitk);
 	sys_tmr2 = immr_map(im_sit);
-	time = mktime(tm->tm_year+1900, tm->tm_mon+1, tm->tm_mday,
-	              tm->tm_hour, tm->tm_min, tm->tm_sec);
+	time = rtc_tm_to_time64(tm);
 
 	out_be32(&sys_tmr1->sitk_rtck, KAPWR_KEY);
-	out_be32(&sys_tmr2->sit_rtc, time);
+	out_be32(&sys_tmr2->sit_rtc, (u32)time);
 	out_be32(&sys_tmr1->sitk_rtck, ~KAPWR_KEY);
 
 	immr_unmap(sys_tmr2);