There is no choice to have the RealView clocks as module for sure,
so turn this config option into a boolean.
Reported-by: NPawel Moll <pawel.moll@arm.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NMike Turquette <mturquette@linaro.org>