frv: Use core allocator for task_struct

There is no point having a copy of the core allocator.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: David Howells <dhowells@redhat.com>
Link: http://lkml.kernel.org/r/20120503085033.967140188@linutronix.de