PDP10: Remove tmxr_input_pending_ln() usage from dpk and tk10 devices

[markpizz]

Learning from the MTY device, remove the non-public routine usage of tmxr_input_pending_ln() from DPK and TK10 devices

[rcornwell]

@larsbrinkhoff This one is for you.

[larsbrinkhoff]

You can assign it to me.

I guess all my TMXR code is due for an overhaul. There are also AUXCPU and TEN11 which works with packets. They send a request on the wire and busy wait for a response. Instead, they could schedule a UNIT to poll for incoming packets.

[larsbrinkhoff]

This will be part of #160.

[larsbrinkhoff]

DPK done in #187. TK work in progress #191.