x86, mrst: Add vrtc platform data setup code

vRTC information is obtained from SFI tables on Moorestown, this patch parses
these tables and assign the information.

Signed-off-by: Feng Tang <feng.tang@intel.com>
LKML-Reference: <43F901BD926A4E43B106BF17856F07559FB80D0D@orsmsx508.amr.corp.intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>