tty: The big operations rework

tty: The big operations rework

- Operations are now a shared const function block as with most other Linux
  objects

- Introduce wrappers for some optional functions to get consistent behaviour

- Wrap put_char which used to be patched by the tty layer

- Document which functions are needed/optional

- Make put_char report success/fail

- Cache the driver->ops pointer in the tty as tty->ops

- Remove various surplus lock calls we no longer need

- Remove proc_write method as noted by Alexey Dobriyan

- Introduce some missing sanity checks where certain driver/ldisc
  combinations would oops as they didn't check needed methods were present

[[email protected]: fix fs/compat_ioctl.c build]
[[email protected]: fix isicom]
[[email protected]: fix arch/ia64/hp/sim/simserial.c build]
[[email protected]: fix kgdb]
Signed-off-by: Alan Cox <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Cc: Jason Wessel <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>