s390/crypto: fix stckf loop

The store-clock-fast loop in generate_entropy() mixes (exors)
only the first 64 bytes of the initial page before doing the
first SHA256. Fix the loop to mix the store-clock-fast values
all over the page.
Signed-off-by: Harald Freudenberger <freude@linux.vnet.ibm.com>
Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/crypto/prng.c

@@ -125,7 +125,7 @@ static int generate_entropy(u8 *ebuf, size_t nbytes)
 		/* fill page with urandom bytes */
 		get_random_bytes(pg, PAGE_SIZE);
 		/* exor page with stckf values */
-		for (n = 0; n < sizeof(PAGE_SIZE/sizeof(u64)); n++) {
+		for (n = 0; n < PAGE_SIZE / sizeof(u64); n++) {
 			u64 *p = ((u64 *)pg) + n;
 			*p ^= get_tod_clock_fast();
 		}