x86, efi: Properly pre-initialize table pointers

Consumers of the table pointers in struct efi check for
EFI_INVALID_TABLE_ADDR to determine validity, hence these
pointers should all be pre-initialized to this value (rather
than zero).

Noticed by the discrepancy between efivars' systab sysfs entry
showing all tables (and their pointers) despite the code
intending to only display the valid ones. No other bad effects
known, but having the various table parsing routines bogusly
access physical address zero is certainly not very desirable
(even though they're unlikely to find anything useful there).

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Link: http://lkml.kernel.org/r/4E13100A020000780004C256@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/platform/efi/efi.c

@@ -51,7 +51,17 @@
 int efi_enabled;
 EXPORT_SYMBOL(efi_enabled);
 
-struct efi efi;
+struct efi __read_mostly efi = {
+	.mps        = EFI_INVALID_TABLE_ADDR,
+	.acpi       = EFI_INVALID_TABLE_ADDR,
+	.acpi20     = EFI_INVALID_TABLE_ADDR,
+	.smbios     = EFI_INVALID_TABLE_ADDR,
+	.sal_systab = EFI_INVALID_TABLE_ADDR,
+	.boot_info  = EFI_INVALID_TABLE_ADDR,
+	.hcdp       = EFI_INVALID_TABLE_ADDR,
+	.uga        = EFI_INVALID_TABLE_ADDR,
+	.uv_systab  = EFI_INVALID_TABLE_ADDR,
+};
 EXPORT_SYMBOL(efi);
 
 struct efi_memory_map memmap;