drivers/rtc: Remove redundant rtc_valid_tm() from rtc_resume()

rtc_read_time() has already judged valid tm by rtc_valid_tm(),
so just remove it.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1427945681-29972-17-git-send-email-john.stultz@linaro.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>