[efi] Use EFI-native mechanism for accessing SMBIOS table

EFI provides a copy of the SMBIOS table accessible via the EFI system
table, which we should use instead of manually scanning through the
F000:0000 segment.

src/config/defaults/efi.h

@@ -14,6 +14,7 @@
 #define TIMER_EFI
 #define NAP_EFIX86
 #define UMALLOC_EFI
+#define SMBIOS_EFI
 
 #define	IMAGE_EFI		/* EFI image support */