Move vTaskPayload from board specific directory to a generic implementation in modules/

[augustofg]

The is a lot of duplicated code on port/board/afc-bpm/v3_1/payload.c, port/board/afc-fofb-ctrl/v3_1/payload.c, port/board/afc-timing/payload.c and port/board/afc-v4/payload.c. This can be unified in a single generic implementation of vTaskPayload that calls board specific functions for managing the payload power.