firmware: dmi_scan: Fix UUID length safety check

The test which ensures that the DMI type 1 structure is long enough
to hold the UUID is off by one. It would fail if the structure is
exactly 24 bytes long, while that's sufficient to hold the UUID.

I don't expect this bug to cause problem in practice because all
implementations I have seen had length 8, 25 or 27 bytes, in line
with the SMBIOS specifications. But let's fix it still.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Fixes: a814c3597a6b ("firmware: dmi_scan: Check DMI structure length")
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/firmware/dmi_scan.c

@@ -186,7 +186,7 @@ static void __init dmi_save_uuid(const struct dmi_header *dm, int slot,
 	char *s;
 	int is_ff = 1, is_00 = 1, i;
 
-	if (dmi_ident[slot] || dm->length <= index + 16)
+	if (dmi_ident[slot] || dm->length < index + 16)
 		return;
 
 	d = (u8 *) dm + index;