CHROMIUM: exynos: dts: ALS configuration is per board

CHROMIUM: exynos: dts: ALS configuration is per board

Move the Ambient Light Sensor configuration to board-specific files.
Only Snow has an ISLxxxx light sensor.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
BUG=chrome-os-partner:17507
TEST=on Snow, boot and check the ambient light sensor is working when
putting the finger on it.
On Spring, boot and observe we no longer have isl driver failure in the kernel log.

Change-Id: I54a3031a4ea211c3a2cd5c56d9188387b329f72a
Reviewed-on: https://gerrit.chromium.org/gerrit/42334
Tested-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Bryan Freed <bfreed@chromium.org>
Commit-Queue: Vincent Palatin <vpalatin@chromium.org>