powerpc: use time64_t in read_persistent_clock

Looking through the remaining users of the deprecated mktime()
function, I found the powerpc rtc handlers, which use it in
place of rtc_tm_to_time64().

To clean this up, I'm changing over the read_persistent_clock()
function to the read_persistent_clock64() variant, and change
all the platform specific handlers along with it.

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

arch/powerpc/platforms/maple/maple.h

@@ -6,7 +6,7 @@
  */
 extern int maple_set_rtc_time(struct rtc_time *tm);
 extern void maple_get_rtc_time(struct rtc_time *tm);
-extern unsigned long maple_get_boot_time(void);
+extern time64_t maple_get_boot_time(void);
 extern void maple_calibrate_decr(void);
 extern void maple_pci_init(void);
 extern void maple_pci_irq_fixup(struct pci_dev *dev);