dt-bindings: vendor-prefixes: Add Lontium vendor prefix

Add prefix for Lontium Semiconductor Corporation

Acked-by: Rob Herring <robh@kernel.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200723163442.1280414-2-vkoul@kernel.org