x86: remove support for non-PAE page tables

PAE tables introduce the NX bit which is very desirable
from a security perspetive, back in 1995.

PAE tables are larger, but we are not targeting x86 memory
protection for RAM constrained devices.

Remove the old style 32-bit tables to make the x86 port
easier to maintain.

Renamed some verbosely named data structures, and fixed
incorrect number of entries for the page directory
pointer table.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>