FPU state is saved into task_struct of created task. Current task continues
use of the state, so it needs TIF_USEDFPU flag is not cleared.

Created task receives fresh FPU and cleared TIF_USEFPU flag is required for it.
Signed-off-by: Kirill Tkhai <tkhai@yandex.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>