platform/x86: thinkpad_acpi: check dytc version for lapmode sysfs

Lenovo platforms with DYTC versions earlier than version 5 don't set
the lapmode interface correctly, causing issues with thermald on
older platforms.

Add checking to only create the dytc_lapmode interface for version
5 and later.

Fixes: 1ac09656

 ("platform/x86: thinkpad_acpi: Add palm sensor support")
Signed-off-by: Mark Pearson <markpearson@lenovo.com>
Link: https://lore.kernel.org/r/20210311174843.3161-1-markpearson@lenovo.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>