Add in missing events for Sandy Bridge Xeon.

* Add in MEM_LOAD_UOPS_LLC_HIT_RETIRED for both sandy bridge and sandy
  bridge Xeon.  Right now it only is enabled for Sandy Bridge.
* D2/0F is actually a combination rather than a separate counter, so
  just flip that on for the CPU types that support it.

There's an errata for using this on SB Xeon hardware - I've documented
it in kern/181346.

Tested:

* Sandy Bridge
* Sandy Bridge Xeon

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