Add the FDT table GUID. This is used to pass the device tree blob from UEFI

to the loader in a similar way to the ACPI tables.

This will be used on arm64 but is not specific to the architecture.

Sponsored by:	The FreeBSD Foundation

sys/boot/efi/include/efiapi.h

@@ -842,6 +842,8 @@ typedef struct {
 #define SAL_SYSTEM_TABLE_GUID    \
   { 0xeb9d2d32, 0x2d88, 0x11d3, 0x9a, 0x16, 0x0, 0x90, 0x27, 0x3f, 0xc1, 0x4d }
 
+#define FDT_TABLE_GUID    \
+  { 0xb1b621d5, 0xf19c, 0x41a5, 0x83, 0x0b, 0xd9, 0x15, 0x2c, 0x69, 0xaa, 0xe0 }
 
 typedef struct _EFI_CONFIGURATION_TABLE {
   EFI_GUID                VendorGuid;