sched: Remove unused 'rq' variable and cpu_rq() call from alloc_fair_sched_group()

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20110323111722.GA4244@swordfish.minsk.epam.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>