hwmon: (adt7310) Use spi_w8r16be() instead spi_w8r16()

Using spi_w8r16be() instead of spi_w8r16() in this driver makes a code a bit
shorter and cleaner.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Mark Brown <broonie@linaro.org>