If this was OpenBSD I would refer you to
http://www.openbsd.org/faq/faq5.html#BootConfig to disable the
05:06.1 SD Host controller: Ricoh Co Ltd R5C822 SD/SDIO/MMC/MS/MSPro Host Adapter (rev 19) which seems to be the culprit.
NetBSD also also allows you disable a device (driver) before booting the kernel. See the
userconf man page. You can see that the commands are similar/equivalent to the OpenBSD ones.
According to this man page the NetBSD user kernel configuration facility was taken from or inspired by the OpenBSD one
So you would have to boot the NetBSD install kernel with "-c" parameter. Unfortunately I have no NetBSD machine available. If you need urgent help on this "sunny" Sunday afternoon you could ask on one of the NetBSD IRC channels. See
http://www.netbsd.org/community/