stand/multiboot2: fix header length check

Check whether we have reached the end of the buffer using search_size
instead of MULTIBOOT_SEARCH, which is the maximum defined by the
specification, but the file can be shorter than that.

This prevents printing a harmless error message when loading a file
that is smaller than MULTIBOOT_SEARCH.

Sponsored by: Citrix Systems R&D
MFC after: 3 days
Fixes: adda2797eb ('stand/multiboot2: add support for booting a Xen dom0 in UEFI mode')

stand/efi/loader/arch/amd64/multiboot2.c

@@ -107,7 +107,7 @@ loadfile(char *filename, uint64_t dest, struct preloaded_file **result)
 			break;
 	}
 
-	if (i >= MULTIBOOT_SEARCH) {
+	if (i >= search_size) {
 		error = EFTYPE;
 		goto out;
 	}