ram: Use page number instead of an address for the bitmap operations

We use an unsigned long for the page number.  Notice that our bitmaps
already got that for the index, so we have that limit.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

--

rename page to page_abs everywhere.
fix trace types for pages
