pmap_mmap

[Masao Uebayashi <uebayasi%tombi.co.jp@localhost>]

I'm re-writing XIP-capable memory disk based on md(4) following
people's suggestions.

md(4) mmap has to return "mdpgno" of char md_root_image[].  I can
get physical address of md_root_image[] by pmap_extract(9).  There's
no API to convert physical address to "mdpgno" (opposite of
pmap_phys_address(9)).

What I ended up is pmap_mmap(9), which is exactly mmmmap(), but
made public.

Does this sound right?