Add checking whether the clock is valid.
Signed-off-by: NSeungwon Jeon <tgih.jun@samsung.com>
Acked-by: NJaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: NAlim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>