Not all platforms support gating the clock, so it is not an error if
the clock does not exist. However, if it does exist, we should
enable/disable it as appropriate.
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Tested-by: NJamie Lentin <jm@lentin.co.uk>
Signed-off-by: NMike Turquette <mturquette@linaro.org>