arm64: dts: khadas-vim3: add support for the SM1 based VIM3L

Add the Amlogic SM1 based Khadas VIM3L, sharing all the same features
as the G12B based VIM3, but:
- a different DVFS support since only a single cluster is available
- audio is still not available on SM1

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>