dt-bindings: arm: amlogic: add Amlogic SM1 based Khadas VIM3L bindings

The Khadas VIM3 is also available as VIM3L with the Pin-to-pin compatible
Amlogic SM1 SoC in the S905D3 variant package.

Change the description to match the S905X3/D3/Y3 variants like the G12A
description, and add the khadas,vim3l compatible.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>