powerpc: Use generic time config

Signed-off-by: Anna-Maria Gleixner <anna-maria@glx-um.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Link: http://lkml.kernel.org/r/20120518163106.464567389@glx-um.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>