staging/fwserial: Update TODO file per reviewer comments

Pursuant to this review https://lkml.org/lkml/2012/11/12/500
by Stefan Richter, update the TODO file.
- Clarify purpose of TODO file
- Remove firewire item #4. As discussed in this conversation
  https://lkml.org/lkml/2012/11/13/564 knowing the AR buffer size
  is not a hard requirement. The required rx buffer size can be
  determined experimentally.
- Remove firewire item #5. This was a private note for further
  experimentation.
- Change firewire item #1. Change suggested header from uapi header
  to kernel-only header.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fwserial/TODO

-TODOs
------
+TODOs prior to this driver moving out of staging
+------------------------------------------------
 1. Implement retries for RCODE_BUSY, RCODE_NO_ACK and RCODE_SEND_ERROR
    - I/O is handled asynchronously which presents some issues when error
      conditions occur.
@@ -11,14 +11,9 @@ TODOs
 -- Issues with firewire stack --
 1. This driver uses the same unregistered vendor id that the firewire core does
      (0xd00d1e). Perhaps this could be exposed as a define in
-     firewire-constants.h?
+     firewire.h?
 3. Maybe device_max_receive() and link_speed_to_max_payload() should be
      taken up by the firewire core?
-4. To avoid dropping rx data while still limiting the maximum buffering,
-     the size of the AR context must be known. How to expose this to drivers?
-5. Explore if bigger AR context will reduce RCODE_BUSY responses
-   (or auto-grow to certain max size -- but this would require major surgery
-    as the current AR is contiguously mapped)
 
 -- Issues with TTY core --
   1. Hack for alternate device name scheme