ntp/pps: replace getnstime_raw_and_real with 64-bit version

There is exactly one caller of getnstime_raw_and_real in the kernel,
which is the pps_get_ts function. This changes the caller and
the implementation to work on timespec64 types rather than timespec,
to avoid the time_t overflow on 32-bit architectures.

For consistency with the other new functions (ktime_get_seconds,
ktime_get_real_*, ...), I'm renaming the function to
ktime_get_raw_and_real_ts64.

We still need to convert from the internal 64-bit type to 32 bit
types in the caller, but this conversion is now pushed out from
getnstime_raw_and_real to pps_get_ts. A follow-up patch changes
the remaining pps code to completely avoid the conversion.

Acked-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>