MdeModulePkg: load boot logo into BGRT table

This is a shoehorned-in implementation of an ACPI BGRT
table, ported pretty much directly from the version used
under CorebootPayloadPkg.

EDK2 provides a facility to do this already, but it assumes
the ACPI tables already exist as EFI structures, so would need
to write code to populate those using the tables already in RAM
created by coreboot. This seemed like the easier option ATM.

Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>

MdeModulePkg/Include/Library/BootLogoLib.h

@@ -61,4 +61,14 @@ BootLogoUpdateProgress (
   IN UINTN                         PreviousValue
   );
 
+/**
+
+  Install Boot Logo into BGRT table
+
+**/
+VOID
+AddBGRT (
+  VOID
+  );
+
 #endif