ARM: OMAP: 32k counter: Provide y2038-safe omap_read_persistent_clock() replacement

ARM: OMAP: 32k counter: Provide y2038-safe omap_read_persistent_clock() replacement

As part of addressing "y2038 problem" for in-kernel uses, this
patch adds the y2038-safe omap_read_persistent_clock64() using
timespec64.

Because we rely on some subsequent changes to convert arm
multiarch support, omap_read_persistent_clock() will be removed
then.

Also remove the needless spinlock, because
read_persistent_clock() doesn't run simultaneously.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1427945681-29972-5-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>