Changelog for 3.0-305

Implement what was done by r9a627e89 using a stub device

This is arguably better then using the slot0 device for slot1, because it maps
the real hardware better (nothing can be mounted on slot1 on a Wii AFAICT).
This also makes Kirby: Return to Dreamland work properly and fixes some of the
SD card problems (libs do not expect to have the same SD card mounted two times
in RW...).