Bug with dynamic payload length and NO_ACK

[arthurxie]

There are two EN_DPL definitions(one with value 0x04, one with value 0x02, the right value is 0x04) with different values. This will make the FEATURE to be set a wrong value.

When I want to send a packet without retransmission, I call radio.setAutoAck(0) and radio.setRetries(0, 0) to disable it. Neither of the two methods set FEATURE's EN_DYN_ACK bit, nor there is a special method to do it. Only the write_register method can be a work around.