random: update comment from copy_to_user() -> copy_to_iter()

This comment wasn't updated when we moved from read() to read_iter(), so
this patch makes the trivial fix.

Fixes: 1b388e77 ("random: convert to using fops->read_iter()")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

drivers/char/random.c

@@ -408,7 +408,7 @@ static ssize_t get_random_bytes_user(struct iov_iter *iter)
 
 	/*
 	 * Immediately overwrite the ChaCha key at index 4 with random
-	 * bytes, in case userspace causes copy_to_user() below to sleep
+	 * bytes, in case userspace causes copy_to_iter() below to sleep
 	 * forever, so that we still retain forward secrecy in that case.
 	 */
 	crng_make_state(chacha_state, (u8 *)&chacha_state[4], CHACHA_KEY_SIZE);