[BOOT] Add EFI headers and entry point

BOOT/ENVIRON/INC/efiprot.h

@@ -0,0 +1,27 @@
+/*++
+
+Copyright (c) 2024, the LibreXP developers.
+Provided under the BSD 3-Clause license.
+
+Module Name:
+
+   efiprot.h
+
+Abstract:
+
+   Provides EFI protocol definitions.
+
+--*/
+
+#ifndef _EFIPROT_H
+#define _EFIPROT_H
+
+/*
+ * Device path protocol definitions.
+ */
+
+#define EFI_DEVICE_PATH_PROTOCOL_GUID \
+    { 0x9576e91, 0x6d3f, 0x11d2, { 0x8e, 0x39, 0x0, 0xa0, 0xc9, 0x69, 0x72, 0x3b } }
+#define DEVICE_PATH_PROTOCOL EFI_DEVICE_PATH_PROTOCOL_GUID
+
+#endif