mfd: Fix off-by-one value range checking for tps65912_i2c_write

If bytes == (TPS6591X_MAX_REGISTER + 1), we have a buffer overflow when
doing memcpy(&msg[1], src, bytes).
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/tps65912-i2c.c

@@ -57,7 +57,7 @@ static int tps65912_i2c_write(struct tps65912 *tps65912, u8 reg,
 	u8 msg[TPS6591X_MAX_REGISTER + 1];
 	int ret;
 
-	if (bytes > (TPS6591X_MAX_REGISTER + 1))
+	if (bytes > TPS6591X_MAX_REGISTER)
 		return -EINVAL;
 
 	msg[0] = reg;