Fix startup crash on externally powered device (Axp)

[wswag]

deleted line SetPeripheralsPower(true) within AXP192::begin() code which causes PowerOff on M5Core2 hardware powered externally via 5V Bus w/o USB cable connected.

The crash is caused by setting EXTEN to 1 within this statement before checking VBUS status if no usb cable is connected. The statement is completely obsolete as EXTEN will be enabled correctly anyway if v-bus status indicates that internal power is required (directly within the following if-statement).

Tested with ext. power, bat power and USB all doing well now.