x86-64: non-paravirt systems always has PSE and PGE

A paravirtualized system may not have PSE or PGE available to
guests, so they are not required features.  However, without
paravirt we can assume that any x86-64 implementation will have
them available.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>