random: convert to ENTROPY_BITS for better code readability

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Link: https://lore.kernel.org/r/20190607182517.28266-2-tiny.windzz@gmail.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

drivers/char/random.c

@@ -760,7 +760,7 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits)
 			if (entropy_bits < 128)
 				return;
 			crng_reseed(&primary_crng, r);
-			entropy_bits = r->entropy_count >> ENTROPY_SHIFT;
+			entropy_bits = ENTROPY_BITS(r);
 		}
 	}
 }
@@ -1378,8 +1378,7 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
 		goto retry;
 
 	trace_debit_entropy(r->name, 8 * ibytes);
-	if (ibytes &&
-	    (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
+	if (ibytes && ENTROPY_BITS(r) < random_write_wakeup_bits) {
 		wake_up_interruptible(&random_write_wait);
 		kill_fasync(&fasync, SIGIO, POLL_OUT);
 	}