bpf: clean up put_cpu_var usage

put_cpu_var takes the percpu data, not the data returned from
get_cpu_var.

This doesn't change the behavior.

Cc: Tejun Heo <tj@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: NShaohua Li <shli@fb.com>
Acked-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

kernel/bpf/core.c

@@ -1031,7 +1031,7 @@ BPF_CALL_0(bpf_user_rnd_u32)
 
 	state = &get_cpu_var(bpf_user_rnd_state);
 	res = prandom_u32_state(state);
-	put_cpu_var(state);
+	put_cpu_var(bpf_user_rnd_state);
 
 	return res;
 }