embedding the address of its xxx_mountroot() in swapnetbsd.c. This
permits booting of kernels with hard-wired filesystem type even if the
filesystem is in a loadable module (ie, not linked into the kernel
image).
Discussed on current-users. Tested on amd64 and i386 with both hard-
wired and '?' filesystem times, and on both modular and monolithic
kernels.
Thanks to pooka@ for code review and suggestions.
Addresses my PR kern/40167