sabrelite HW setup: mention SW1 position for old boards

SabreLite v1.0 has a reversed switch position for SW1 for
normal and USB-OTG boot. Since it is very rare and old board
there is no need to provide the photo but it is useful to mention
about the difference.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>