The board should not globally set `TERMFLAGS` without a RIOT_TERMINAL
condition.
Also the board does not export uart through usb and thus needs an uart
converter connected. Other boards in the same situation do not need
to set `TERMPROG` without a valid baudrate. So remove the definition
anyway.
This also removes the export of TERM* variables and should make it work
with the other RIOT_TERMINAL.
Includes of $(CPU)/include and $(BOARD)/include and already added in the
main Makefile.include.
Verification:
There are no common headers names between boards and cpus.
Except native that has a 'periph_conf.h' in cpu instead of being in board.
