ieee802154: ensure that first RF212 state comes from TRX_OFF

A documented erratum of the RF212 chip describes that some versions of
RF212 may not be properly reset by the standard reset procedure. The
described workaround seems to not fully work either; my RF212 chips will
not correctly receive any frames unless they are taken from RX mode to
TRX_OFF and back to RX mode, effectively forcing a up-down-up-cycle.
Going to TRX_OFF and to RX without intermediate state changes at least
once fixes this.

The same transition is allowed for RF230, so simply do it all the time.

Signed-off-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>