Add utility to calculate only the SinitMleData.SinitHash.

This was needed / useful to just identify the SINIT ACM that's been
loaded.  txt-stat doesn't have any concept of file names so this is
the only way I know of to link an SINIT from file to the one that
tboot has used to set up the MLE.
.
Conditionally hash OsSinitData.Capabilities or 0's based on LCP PolicyControl field.