patch - at91 serial drivers assumed realtime response for DSR routines

[Jani Monoses]

> The at91 serial routines are broken in that they assume a very low
> latency for the DSR handler.

The patch you sent is specific to your setup right, it's not a clean
update to at91 serial? I see hw flowcontrol and line status code is
there but the at91 does not have such capabilities.
I just mention this so that whoever else sees the patch knows that a
patch which would just improve upon the current driver without the 
16650 support would be smaller and cleaner :)

Jani