Signature of RTCT ACPI table maybe "PTCT"(v1) or "RTCT"(v2).
and the MAGIC number in CRL header is also changed from "PTCM"
to "RTCM".
This patch refine the code to detect RTCT table for both
v1 and v2.
Tracked-On: #6020
Signed-off-by: Yonghua Huang <yonghua.huang@intel.com>