hwmon: (w83627ehf) make sensor_dev_attr_##_name variables static

hwmon: (w83627ehf) make sensor_dev_attr_##_name variables static

Fix sparse warning:

drivers/hwmon/w83627ehf.c:1202:1: warning:
	symbol 'sensor_dev_attr_pwm1_target' was not declared. Should it be static?

and many more similar messages.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
Link: https://lore.kernel.org/r/20191213015605.172472-1-chenzhou10@huawei.com
[groeck: Dropped all but one log message from description]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>