HEADS UP: MIPS switching to common pmap (uvm/pmap)

[Matt Thomas <matt%3am-software.com@localhost>]

I now have MIPS using the same pmap code as PowerPC BookE in sys/uvm/pmap.  

I plan on merging it into the tree next week.  I’ve tested it on ERLITE, MALTA, and 
TWRP1025 but I’m sure there are going to some issues.

If you have a MIPS system and you’d like to try a new kernel, let me know and I can 
build you one to try.

For those using 64-bit CPUs, using N32 for the kernel will give a decided performance 
boost.  N32 kernels run with a full 64-bit address.  bus_space, the cache routines, and 
the page zero and copy routines have been updated to take and use 64-bit direct 
mapped addresses whenever possible.  This means the N32 kernels can use more 
memory than fits in KSEG0.  

For MIPS3+ and MIPSNN, the default page size has been changed to 8KB which 
speeds the kernel.  The locore routines for mips3 have been updated to use 
mipsNNr2 instructions to increase speed.

By using the common pmap code, MIPS kernel now support dynamically increasing
kernel address space.