ARM, clocksource/drivers: Provide read_boot_clock64() and read_persistent_clock64() and use them

As part of addressing "y2038 problem" for in-kernel uses, this
patch converts read_boot_clock() to read_boot_clock64() and
read_persistent_clock() to read_persistent_clock64() using
timespec64 by converting clock_access_fn to use timespec64.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Thierry Reding <treding@nvidia.com> (for tegra part)
Cc: Russell King <rmk@dyn-67.arm.linux.org.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1427945681-29972-7-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/clocksource/tegra20_timer.c

@@ -141,14 +141,6 @@ static void tegra_read_persistent_clock64(struct timespec64 *ts)
 	*ts = persistent_ts;
 }
 
-static void tegra_read_persistent_clock(struct timespec *ts)
-{
-	struct timespec ts64;
-
-	tegra_read_persistent_clock64(&ts64);
-	*ts = timespec64_to_timespec(ts64);
-}
-
 static unsigned long tegra_delay_timer_read_counter_long(void)
 {
 	return readl(timer_reg_base + TIMERUS_CNTR_1US);
@@ -259,7 +251,7 @@ static void __init tegra20_init_rtc(struct device_node *np)
 	else
 		clk_prepare_enable(clk);
 
-	register_persistent_clock(NULL, tegra_read_persistent_clock);
+	register_persistent_clock(NULL, tegra_read_persistent_clock64);
 }
 CLOCKSOURCE_OF_DECLARE(tegra20_rtc, "nvidia,tegra20-rtc", tegra20_init_rtc);