x86/efi: Free efi_pgd with free_pages()

The efi_pgd is allocated as PGD_ALLOCATION_ORDER pages and therefore must
also be freed as PGD_ALLOCATION_ORDER pages with free_pages().

Fixes: d9e9a64 ("x86/mm/pti: Allocate a separate user PGD")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1521746333-19593-1-git-send-email-longman@redhat.com

arch/x86/platform/efi/efi_64.c

@@ -227,7 +227,7 @@ int __init efi_alloc_page_tables(void)
 	if (!pud) {
 		if (CONFIG_PGTABLE_LEVELS > 4)
 			free_page((unsigned long) pgd_page_vaddr(*pgd));
-		free_page((unsigned long)efi_pgd);
+		free_pages((unsigned long)efi_pgd, PGD_ALLOCATION_ORDER);
 		return -ENOMEM;
 	}