OvmfPkg: Create platform OvmfXen

OvmfXen is a copy of OvmfX64, removing VirtIO and some SMM.

This new platform will be changed to make it works on two types of Xen
guest: HVM and PVH.

Compare to OvmfX64, this patch:

- changed: PLATFORM_GUID, OUTPUT_DIRECTORY, FLASH_DEFINITION
- removed: VirtioLib class resolution
- removed: all UEFI_DRIVER modules for virtio devices
- removed: DXE_SMM_DRIVER and SMM_CORE lib class resolutions
- removed: DXE_SMM_DRIVER and SMM_CORE FDF rules
- removed: Everything related to SMM_REQUIRE==true
- removed: Everything related to SECURE_BOOT_ENABLE==true
- removed: Everything related to TPM2_ENABLE==true
- changed: PcdPciDisableBusEnumeration dynamic default flipped to TRUE
- changed: default FD_SIZE_IN_KB to 2M.
- reverted d272449, "OvmfPkg: raise DXEFV size to 11 MB"

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1689
Signed-off-by: Anthony PERARD <[email protected]>
Reviewed-by: Laszlo Ersek <[email protected]>
Message-Id: <[email protected]>

Maintainers.txt

@@ -372,6 +372,7 @@ F: OvmfPkg/Library/PlatformBootManagerLib/BdsPlatform.c
 F: OvmfPkg/Library/XenConsoleSerialPortLib/
 F: OvmfPkg/Library/XenHypercallLib/
 F: OvmfPkg/Library/XenIoMmioLib/
+F: OvmfPkg/OvmfXen.*
 F: OvmfPkg/PlatformPei/MemDetect.c
 F: OvmfPkg/PlatformPei/Platform.*
 F: OvmfPkg/PlatformPei/Xen.*