mac802154: tx: remove xmit channel context switch

This patch removes the channel hopping feature before xmit. There are
several issues to provide a real channel hopping (timing requirements,
etc...).

We don't have any known kernelspace protocol which really use this
feature. And I don't know an real user of this feature.
We simply drop this feature now.

This patch removes also the hold of pib lock which isn't needed by any
real driver xmit callback implementation.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/include/net/mac802154.h b/include/net/mac802154.h
index b07d431..ba8ddff7 100644
--- a/include/net/mac802154.h
+++ b/include/net/mac802154.h
@@ -113,8 +113,7 @@
  *	  skb cntains the buffer starting from the IEEE 802.15.4 header.
  *	  The low-level driver should send the frame based on available
  *	  configuration.
- *	  This function should return zero or negative errno. Called with
- *	  pib_lock held.
+ *	  This function should return zero or negative errno.
  *
  * ed:    Handler that 802.15.4 module calls for Energy Detection.
  *	  This function should place the value for detected energy