clarify eth driver halt/recv steps

The dev->halt() func can be called at any time, and the dev->recv() func
does not need to use NetRxPackets[] when calling NetReceive().

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>

doc/README.drivers.eth

@@ -122,10 +122,12 @@ function can be called multiple times in a row.
 
 The recv function should process packets as long as the hardware has them
 readily available before returning.  i.e. you should drain the hardware fifo.
-The common code sets up packet buffers for you already (NetRxPackets), so there
-is no need to allocate your own.  For each packet you receive, you should call
-the NetReceive() function on it with the packet length.  So the pseudo code
-here would look something like:
+For each packet you receive, you should call the NetReceive() function on it
+along with the packet length.  The common code sets up packet buffers for you
+already in the .bss (NetRxPackets), so there should be no need to allocate your
+own.  This doesn't mean you must use the NetRxPackets array however; you're
+free to call the NetReceive() function with any buffer you wish.  So the pseudo
+code here would look something like:
 int ape_recv(struct eth_device *dev)
 {
 	int length, i = 0;
@@ -145,7 +147,8 @@ int ape_recv(struct eth_device *dev)
 }
 
 The halt function should turn off / disable the hardware and place it back in
-its reset state.
+its reset state.  It can be called at any time (before any call to the related
+init function), so make sure it can handle this sort of thing.
 
 So the call graph at this stage would look something like:
 some net operation (ping / tftp / whatever...)