Add info for getting the firmware directly from the UEFI for the Chuwi Hi10
Plus (CWI527), so that the user does not need to manually install the
firmware in /lib/firmware/silead.

This change will make the touchscreen on these devices work OOTB,
without requiring any manual setup.

Also tweak the min and width/height values a bit for more accurate position
reporting.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210905130210.32810-2-hdegoede@redhat.com