ARM: dts: sd-600eval: enable 1.8v regulator on LS expansion

This patch enables 1.8v regulator on LS expansion, which should be
always on according to 96boards spec.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>