x86: fix memory ranges in mm documentation

This is a trivial fix to correct upper bound addresses to always be
inclusive. Previously, the majority of ranges specified were inclusive with a
small minority specifying an exclusive upper bound. This patch fixes this
inconsistency.

Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>