- Make DellEMC platform modules Python3 compliant.
- Change return type of PSU Platform APIs in DellEMC Z9264, S5232 and Thermal Platform APIs in S5232 to 'float'.
- Remove multiple copies of pcisysfs.py.
- PEP8 style changes for utility scripts.
- Build and install Python3 version of sonic_platform package.
- Fix minor Platform API issues.
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
