Update DXE Core to be compatible with PI 1.2 SMM Drivers.

Update DXE Core to be compatible with PI 1.2 SMM Drivers.

PI 1.2 SMM Drivers are allowed to call UEFI/DXE services and Protocols from the entry point of the PI 1.2 SMM Driver.  These UEFI/DXE services and Protocols may directly or indirectly calls the UEFI Boot Services RaiseTPL() and RestoreTPL().  These UEFI Boot Services use the CPU Architectural Protocol to enable interrupts if the TPL level is below TPL_HIGH_LEVEL and enable interrupts of the TPL is at TPL_HIGH_LEVEL.  Interrupts should be masked while executing SMM drivers, so if a direct or indirect call to the UEFI Boot Service RestoreTPL() would enable interrupts, then an interrupt could be incorrectly delivered in SMM context.

The solution is for the DXE Core to register for the PI 1.2 SMM Base2 Protocol.  If that protocol is present in the platform, then the DXE Core can use the SMM Base 2 Protocol's InSmm() function to determine if the platform is currently executing in SMM content.  If the current context is in SMM, then do not allow any requests to be forwarded to the CPU Architecture Protocol to enable interrupts.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@9997 6f19259b-4bc3-4df7-8a09-765794883524