DeviceSettings: Add WIFI PM mode toggle

Switch between PM_FAST AND PM_MAX, with PM_FAST being the default. When checkbox is ticked, it switches to PM_MAX mode.

PM_FAST : faster internet speed, higher power consumption
PM_MAX : slower internet speed, lower power consumption

Needs https://github.com/TeamCanjica/Samsung_STE_Kernel/pull/5 to allow toggling of PM mode.