Reduce number of traces in PNOR mbox
Reduce number of traces in PNOR mbox

 - When running with full traces on, the number of
   PNOR traces will overflow the amount of memory
   HB has available.

Change-Id: I4a99794049e7d71138c404f5e3db3ef888c0089b
CQ: SW404627
Backport: release-op910
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/48265
Reviewed-by: William G. Hoffa <7dd6aa5e78423995d9d7c7ecada5b77ee07f88cc@us.ibm.com>
Tested-by: Jenkins Server <8e3f934e4c44875bc48d33da3ea13d93ba9a233f@us.ibm.com>
Tested-by: Jenkins OP Build CI <e610bd72261d3c0a48f1e8ae36832ab00774d426@us.ibm.com>
Tested-by: Jenkins OP HW <0eb0fff262f74a65a832afbcc7b153e391c9a3fd@us.ibm.com>
Reviewed-by: STEWART E. SMITH <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>
Reviewed-by: Daniel M. Crowell <912029ca9254ac7b5854e56910561d682e1fa2d0@us.ibm.com>

open-power/hostboot,open-power/hostboot,open-power/hostboot,open-power/hostboot,open-power/hostboot