softlockup: minor cleanup, don't check task->state twice

The recent commit 16d9679f33caf7e683471647d1472bfe133d858 changed
check_hung_task() to filter out the TASK_KILLABLE tasks. We can
move this check to the caller which has to test t->state anyway.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>