NetBSD 9.2 Cobalt RestoreCD/RestoreUSB

I've updated and put cobalt restorecd images for NetBSD/cobalt 9.2:

 https://cdn.NetBSD.org/pub/NetBSD/arch/cobalt/restore-cd/9.2/

- restorecd-9.2-20210807.iso.gz is a gzipped RestoreCD ISO9660 image.
- restoreusb-9.2-20210807.img.gz is a gzipped RestoreUSB image
  for >=800MiB USB memory sticks on USB bootable PCs.

No functional changes RestoreCD/USB except minor fixes:
 https://github.com/tsutsui/netbsd-cobalt-restorecd
and briefly tested on Qube 2:
 https://dmesgd.nycbug.org/index.cgi?do=view&id=6205

See also "Restore CD/USB Howto" for actual installation procedures:
 https://www.NetBSD.org/ports/cobalt/restorecd-howto.html

Have fun, 
---
Izumi Tsutsui