platform/x86: silead_dmi: Add Teclast X3 Plus tablet support

Add touchscreen platform data for the Teclast X3 Plus tablet.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Alberto Ponces <ponces26@gmail.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>