i2c: npcm7xx: Fix timeout calculation

timeout_usec value calculation was wrong, the calculated value
was in msec instead of usec.

Fixes: 56a1485b ("i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver")
Signed-off-by: Tali Perry <tali.perry1@gmail.com>
Reviewed-by: Avi Fishman <avifishman70@gmail.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Alex Qiu <xqiu@google.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-npcm7xx.c

@@ -2093,8 +2093,12 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 		}
 	}
 
-	/* Adaptive TimeOut: astimated time in usec + 100% margin */
-	timeout_usec = (2 * 10000 / bus->bus_freq) * (2 + nread + nwrite);
+	/*
+	 * Adaptive TimeOut: estimated time in usec + 100% margin:
+	 * 2: double the timeout for clock stretching case
+	 * 9: bits per transaction (including the ack/nack)
+	 */
+	timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite);
 	timeout = max(msecs_to_jiffies(35), usecs_to_jiffies(timeout_usec));
 	if (nwrite >= 32 * 1024 || nread >= 32 * 1024) {
 		dev_err(bus->dev, "i2c%d buffer too big\n", bus->num);