soc/intel/skylake: Implement Global Reset MEI message

soc/intel/skylake: Implement Global Reset MEI message

As per ME BWG, there are two mechanism to generate a Global
Reset (resets both host and Intel ME), one is through CF9h
IO write of 6h or Eh with "CF9h Global Reset" (CF9GR) bit set,
PMC PCI offset ACh[20]. Another is to issue the Global Reset
MEI message. Because any attempts to cause global reset without
synchronizing the two sides might cause unwanted side effects,
such as unwritten flash data that will get destroyed if the
host were to cause a global reset without informing Intel ME
firmware, the recommended method is to send a Global Reset MEI
message when the following conditions are met:

The PCH chipset firmware just needs to complete the Intel ME
Interface #1 initialization and check the Intel ME HFSTS state
if Intel ME is not in ERROR state and is accepting MEI commands
then firmware should be able to use Global Reset MEI message to
trigger global reset.

Furthermore, if Intel ME is in ERROR state, BIOS can use I/O 0xCF9
write of 0x06 or 0x0E command with PCH ETR3 register bit [20]
to perform the global reset.

BUG=none
BRANCH=none
TEST=Verified Global Reset MEI message is able to perform platform
global issue in ME good state.

Change-Id: If326a137eeadaa695668b76b84c510e12c546024
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Signed-off-by: Rizwan Qureshi <rizwan.qureshi@intel.com>
Reviewed-on: https://review.coreboot.org/16902
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>