hwrng: core - correct error check of kthread_run call

The kthread_run() function can return two different error values
but the hwrng core only checks for -ENOMEM. If the other error
value -EINTR is returned it is assigned to hwrng_fill and later
used on a kthread_stop() call which naturally crashes.

Cc: [e-mail]
Signed-off-by: Martin Schwidefsky <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/char/hw_random/core.c

···
 static void start_khwrngd(void)
 {
 	hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
-	if (hwrng_fill == ERR_PTR(-ENOMEM)) {
+	if (IS_ERR(hwrng_fill)) {
 		pr_err("hwrng_fill thread creation failed");
 		hwrng_fill = NULL;
 	}