hwmon: Drop obsolete JZ4740 driver

The JZ4740 boards now use the iio-hwmon driver.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Artur Rojek <contact@artur-rojek.eu>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Paul Burton <paul.burton@mips.com>