Fix 259 alerts reported by the LGTM tool:
- 245 for Unused import
- 7 for Testing equality to None
- 5 for Duplicate key in dict literal
- 1 for Module is imported more than once
- 1 for Unused local variable
1. undefine led_classdev_register as it is defined in leds.h
2. header file location change
a. linux/i2c/pmbus.h -> linux/pmbus.h
b. linux/i2c-mux-gpio.h -> linux/platform_data/i2c-mux-gpio.h
c. linux/i2c/pca954x.h -> linux/platform_data/pca954x.h
