Reconfigure PAT to permit write-combining memory type to be assigned
on a page-by-page basis. Changes PWT and PCD bit combinations in page
table entries so that they correspond to the following format:
PAT
|PCD
||PWT
|||
000 WB Write Back (WB)
001 WC Write Combining (WC)
010 UC- Uncached (UC-)
011 UC Uncacheable (UC)
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