staging: octeon-ethernet: add TODO

Add missing TODO to describe the plan to get this driver out of staging.
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/octeon/TODO

+This driver is functional and supports Ethernet on OCTEON+/OCTEON2/OCTEON3
+chips at least up to CN7030.
+
+TODO:
+	- general code review and clean up
+	- make driver self-contained instead of being split between staging and
+	  arch/mips/cavium-octeon.
+
+Contact: Aaro Koskinen <aaro.koskinen@iki.fi>