From: Alban Bedel <redacted>
Date: Tue, 28 Feb 2017 18:08:55 +0100

On DT systems the driver require a clock, but the probe just print a
warning and continue, leading to a crash when resetting the device.
To fix this crash and properly handle probe deferals only ignore the
missing clock if DT isn't used or if the clock doesn't exist.

Signed-off-by: Alban Bedel <redacted>

Applied, thanks.