ARM: versatile: Don't use platform clock for Integrator & VE

Due to automatic merge of a613163dff04cbfcb7d66b06ef4a5f65498ee59b
"ARM: integrator: convert to common clock" and
56a34b03ff427046494db87f05fc810aaedd23a5 "ARM: versatile: Make
plat-versatile clock optional" two platforms: Integrator and
Versatile Express now select both COMMON_CLK and
PLAT_VERSATILE_CLOCK which breaks building them. Fixed now.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>