tokenring: delete all remaining driver support

This represents the mass deletion of the of the tokenring support.

It gets rid of:
  - the net/tr.c which the drivers depended on
  - the drivers/net component
  - the Kbuild infrastructure around it
  - any tokenring related CONFIG_ settings in any defconfigs
  - the tokenring headers in the include/linux dir
  - the firmware associated with the tokenring drivers.
  - any associated token ring documentation.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>