hmp: Name HMP command handler functions hmp_COMMAND()

hmp: Name HMP command handler functions hmp_COMMAND()

Some are called do_COMMAND() (old ones, usually), some hmp_COMMAND(),
and sometimes COMMAND pointlessly differs in spelling.

Normalize to hmp_COMMAND(), where COMMAND is exactly the command name
with '-' replaced by '_'.

Exceptions:

* do_device_add() and client_migrate_info() *not* renamed to
  hmp_device_add(), hmp_client_migrate_info(), because they're also
  QMP handlers.  They still need to be converted to QAPI.

* do_memory_dump(), do_physical_memory_dump(), do_ioport_read(),
  do_ioport_write() renamed do hmp_* instead of hmp_x(), hmp_xp(),
  hmp_i(), hmp_o(), because those names are too cryptic for my taste.

* do_info_help() renamed to hmp_info_help() instead of hmp_info(),
  because it only covers help.

Signed-off-by: Markus Armbruster <armbru@redhat.com>