hm2_pktUART: Various bugfixes and additional queued reads and writes

Queued reads and writes are much better suited to operation with Ethernet and
parallel port devices.
Also add the Rx and Tx status registers to the regular TRAM reads to be immediately
available.
Document the changes and delete the old (too terse) docs.


Signed-off-by: andypugh <andy@bodgesoc.org>

Author: andypugh