[BOOT] Add EFI headers and entry point

BOOT/ENVIRON/INC/efi.h

@@ -0,0 +1,32 @@
+/*++
+
+Copyright (c) 2024, the LibreXP developers.
+Provided under the BSD 3-Clause license.
+
+Module Name:
+
+   efi.h
+
+Abstract:
+
+   Provides EFI header files.
+
+--*/
+
+#ifndef _EFI_H
+#define _EFI_H
+
+#if defined(__x86_64__)
+#include "AMD64/efibind.h"
+#else
+#error Unsupported architecture
+#endif
+
+#include "efidef.h"
+#include "efidevp.h"
+#include "efiprot.h"
+#include "eficon.h"
+#include "efiapi.h"
+#include "efierr.h"
+
+#endif