Fix rounding error in memory allocation code
Fix rounding error in memory allocation code

A rounding error exposed by a new compiler caused us to write
over the SPTE entries for the extended memory block.  This
led to unhandled page faults due to invalid permissions on the
affected pages.

Change-Id: I53656103252180d37a4291176d45f2cb3f63421d
Backport: yes
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/22560
Reviewed-by: Andrew J. Geissler <c46de238cd554860f0bd4010b1729f1323facd9c@us.ibm.com>
Tested-by: Jenkins Server
Tested-by: FSP CI Jenkins
Reviewed-by: William G. Hoffa <7dd6aa5e78423995d9d7c7ecada5b77ee07f88cc@us.ibm.com>

Over-enthusiastic/hostboot,Over-enthusiastic/hostboot,Over-enthusiastic/hostboot,Over-enthusiastic/hostboot,Over-enthusiastic/hostboot