OvmfPkg/EnrollDefaultKeys: extract MICROSOFT_VENDOR_GUID

The GUID

  77FA9ABD-0359-4D32-BD60-28F4E78F784B

is specified in MSDN, at
<https://msdn.microsoft.com/en-us/ie/dn932805(v=vs.94)>, therefore it
deserves an entry in the package DEC file, and a header file under
"Include/Guid".

(Arguably, this GUID declaration / definition could even live under
SecurityPkg, but the edk2 tradition has been to hoist GUIDs,
protocols/PPIs, and lib classes from OvmfPkg to a core package only when
dependent C code is added to the core package.)

Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Julien Grall <julien.grall@arm.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=1747
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Gary Lin <glin@suse.com>

OvmfPkg/OvmfPkg.dec

@@ -77,6 +77,7 @@
   gQemuRamfbGuid                      = {0x557423a1, 0x63ab, 0x406c, {0xbe, 0x7e, 0x91, 0xcd, 0xbc, 0x08, 0xc4, 0x57}}
   gXenBusRootDeviceGuid               = {0xa732241f, 0x383d, 0x4d9c, {0x8a, 0xe1, 0x8e, 0x09, 0x83, 0x75, 0x89, 0xd7}}
   gRootBridgesConnectedEventGroupGuid = {0x24a2d66f, 0xeedd, 0x4086, {0x90, 0x42, 0xf2, 0x6e, 0x47, 0x97, 0xee, 0x69}}
+  gMicrosoftVendorGuid                = {0x77fa9abd, 0x0359, 0x4d32, {0xbd, 0x60, 0x28, 0xf4, 0xe7, 0x8f, 0x78, 0x4b}}
 
 [Protocols]
   gVirtioDeviceProtocolGuid           = {0xfa920010, 0x6785, 0x4941, {0xb6, 0xec, 0x49, 0x8c, 0x57, 0x9f, 0x16, 0x0a}}