efi: Check EFI revision in setup_efi_vars

We need to check the runtime sys_table for the EFI version the firmware
specifies instead of just checking for a NULL QueryVariableInfo.  Older
implementations of EFI don't have QueryVariableInfo but the runtime is
a smaller structure, so the pointer to it may be pointing off into garbage.

This is apparently the case with several Apple firmwares that support EFI
1.10, and the current check causes them to no longer boot.  Fix based on
a suggestion from Matthew Garrett.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 41de115..35ee62f 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -258,7 +258,7 @@
 	u64 store_size, remaining_size, var_size;
 	efi_status_t status;
-	if (!sys_table->runtime->query_variable_info)
+	if (sys_table->runtime->hdr.revision < EFI_2_00_SYSTEM_TABLE_REVISION)
 	data = (struct setup_data *)(unsigned long)params->hdr.setup_data;