Set response size equal to request size for FSP messages
Set response size equal to request size for FSP messages

The Generic FSP message protocol that goes over the mailbox
uses a single buffer for the request and the response.  The PHYP
code enforces this and will reject messages where the two buffer
sizes are not equal.

Change-Id: I338f4c999305b4f5a4ea3660c037978b38882605
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/50959
Tested-by: Jenkins Server <8e3f934e4c44875bc48d33da3ea13d93ba9a233f@us.ibm.com>
Tested-by: Jenkins OP Build CI <e610bd72261d3c0a48f1e8ae36832ab00774d426@us.ibm.com>
Tested-by: FSP CI Jenkins <aa9e4d9ac7cd25905e9c0dd36d4150516e73dd86@us.ibm.com>
Reviewed-by: Elizabeth K. Liner <2cf7b278f097e7e2abe996aafb02aa8116b785d6@us.ibm.com>
Reviewed-by: Roland Veloz <768fb49134ab823c765de70e7067d9f65f5d0a3e@us.ibm.com>
Tested-by: Jenkins OP HW <0eb0fff262f74a65a832afbcc7b153e391c9a3fd@us.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