Fix: Standby after regular write cmd

Realized that the normal write command should always drop to standby-I
mode immediately since the FIFO cannot be filled using this method, and
TX will be complete.

RF24.cpp

@@ -455,6 +455,8 @@ bool RF24::write( const void* buf, uint8_t len )
 	//If autoAck is ON, a payload has to be written prior to reading a payload, else write after reading a payload
 	while( ! ( get_status()  & ( _BV(TX_DS) | _BV(MAX_RT) ))) { }
 
+	ce(LOW); //Set the radio back to STANDBY-I mode since we can only fill one buffer at a time using this method, and tx is complete
+
 	uint8_t status = write_register(STATUS,_BV(RX_DR) | _BV(TX_DS) | _BV(MAX_RT) );
 
   //Max retries exceeded

RF24.h

@@ -354,7 +354,9 @@ public:
    * the manufacturer to drop the radio out of TX or STANDBY-II mode if there is
    * time enough between sends for the FIFOs to empty.
    *
-   * @note This does NOT need to be called when using per-payload noACK commands.
+   * @note This does NOT need to be called when using per-payload noACK commands,
+   * or when using the regular write command since it is only capable of single
+   * payload transmission..
    * Per the datasheet, the radio will automatically engage STANDBY-I mode when
    * using the W_TX_PAYLOAD_NOACK command.
    *