nouveau/vmm: rewrite pte tracker using a struct and bitfields.

nouveau/vmm: rewrite pte tracker using a struct and bitfields.

I want to increase the counters here and start tracking LPTs as well
as there are certain situations where userspace with mixed page sizes
can cause ref/unrefs to live longer so need better reference counting.

This should be entirely non-functional.

Reviewed-by: Mary Guillemard <mary@mary.zone>
Tested-by: Mary Guillemard <mary@mary.zone>
Tested-by: Mel Henning <mhenning@darkrefraction.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patch.msgid.link/20260204030208.2313241-2-airlied@gmail.com