sched, powerpc: Fix sched.h split-up build failure

Fix PowerPC/Cell build fallout from:

  8bd75c77 sched/rt: Move rt specific bits into new header file

Reported-by: Michael Ellerman <michael@ellerman.id.au>
Cc: Clark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20130207094707.7b9f825f@riff.lan


Signed-off-by: Ingo Molnar <mingo@kernel.org>