ARM: ux500: Stop populating the PRCMU devices early

The PRCMU devices are getting populated from the MFD
driver and that is enough for them to come up. We already
have an early quirk for the things that need to happen
really early and the PRCMU timer that need to be registered
really early will find its own node just fine as the
timer/clocksource subsystem looks through the whole device
tree for compatible nodes.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>