[baseimage]: upgrade base image to debian buster
bring up the base image to debian buster 4.19 kernel.
using the merge commits to preserve the individual commits to better track the history.
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
