efi: Process the MEMATTR table only if EFI_MEMMAP is enabled

Otherwise e.g. Xen dom0 on x86_64 EFI platforms crashes.

In theory we can check EFI_PARAVIRT too, however,
EFI_MEMMAP looks more targeted and covers more cases.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: andrew.cooper3@citrix.com
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: linux-efi@vger.kernel.org
Cc: matt@codeblueprint.co.uk
Cc: stable@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1498128697-12943-2-git-send-email-daniel.kiper@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/firmware/efi/efi.c

@@ -528,7 +528,8 @@ int __init efi_config_parse_tables(void *config_tables, int count, int sz,
 		}
 	}
 
-	efi_memattr_init();
+	if (efi_enabled(EFI_MEMMAP))
+		efi_memattr_init();
 
 	/* Parse the EFI Properties table if it exists */
 	if (efi.properties_table != EFI_INVALID_TABLE_ADDR) {