at86rf230: rework transmit and receive handling

This patch is a complete reimplementation of transmit and receive
handling for the at86rf230 driver.

It solves also six bugs:

First:

The RX_SAFE_MODE is enabled and the transceiver doesn't leave the
receive state while the framebuffer isn't read by a CMD_FB command.
This is useful to read out the frame and don't get into another receive
or transmit state, otherwise the frame would be overwritten.
The current driver do twice CMD_FB calls, the first one leaves the
this protection.

Second:

Sometimes the CRC calculation is correct and the length field is above
127. The current mac802154 layer and filter of a at86rf2xx doesn't check
on this and the kernel crashes. In this case the frame is corrupted, we
send the whole receive buffer to the next layer which can be useful for
sniffing.

Thrid:
There is a undocumented race condition. When we are go into the
RX_AACK_ON state the transceiver could be changed into RX_AACK_BUSY
state. This is a normal behaviour. In this case the transceiver received
a SHR while assert wasn't finished.

Fourth:
It also handle some more "correct" state changes. In aret mode the
transceiver need to go to TX_ON before the transceiver go into
RX_AACK_ON.

Fifth:
The programming model [0] describes also a error handling in ARET mode
if the trac status is different than zero. This is patch adds support
for handling this.

Sixth:
In receive handling the transceiver should also get the trac status
according [0]. The driver could use the trac status as error statistic
handling, but the driver doesn't use this currently. There is maybe some
timing behaviour or the read of this register change some transceiver
states.

In addition the irqworker is removed. Instead we do async spi calls and
no scheduling is involved anymore. The transmit function is also
asynchron but with a wait_for_completion handling. The mac802154 layer
doesn't support asynchron transmit handling right now.

The state change behaviour is now changes, before it was:

1. assert while(!STATE_TRANSITION_IN_PROGRESS)
2. state change
3. assert while(!STATE_TRANSITION_IN_PROGRESS)
4. assert once(wanted state != current state)

Sometimes a unexcepted state change occurs when 4. assert was violated.
The new state change behaviour is:

1. assert while(!STATE_TRANSITION_IN_PROGRESS)
2. wait state change timing according datasheet
3. assert once(wanted state != current state)

This behaviour is described in the at86rf231 software programming model [0].
The state change documentation in this programming guide should also valid for
at86rf212 and at86rf233 chips.

The transceiver don't do a FORCE_TX_ON while we want to transmit a PDU.
The new behaviour is a TX_ON and wait a receiving time (tFrame + tPAck).
If we are still in RX_AACK_BUSY then we transmit a FORCE_TX_ON as timeout
handling. The different is that FORCE_TX_ON aborts receiving and TX_ON
waits if RX_AACK_BUSY is finished. This should decrease the drop rate of
packets.

[0] http://www.atmel.com/Images/AVR2022_swpm231-2.0.zip
at86rf230: move RX_SAFE_MODE setting to hw_init

There is no need to set this bit in start callback which could be
called more than once.
at86rf230: rework irq_pol setting

This patch rework the irq_pol register setting for rising and falling
interrupt settings only. The default behaviour should be rising flag.

Also use IRQ_TYPE_* defines instead of IRQF_* defines. There is no
functionality change but irq_get_trigger_type returns IRQ_TYPE_* defines.
at86rf230: rework state change and start/stop

This patch removes the current synchron state change function and add a
new function for a state assert. Change the start and stop callbacks to
use this new synchron state change behaviour. It's a wrapper around the
async state change function.
at86rf230: rework reset to trx_off state change
at86rf230: add timing for channel switch
at86rf230: add sleep cycle timing
at86rf230: add new author