timekeeping: Prints the amounts of time spent during suspend

In addition to keeping a histogram of suspend times, also
print out the time spent in suspend to dmesg.

This helps to keep track of suspend time while debugging using
kernel logs.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Ruchi Kandoi <kandoiruchi@google.com>
[jstultz: Tweaked commit message]
Signed-off-by: John Stultz <john.stultz@linaro.org>