ARM: socfpga: dts: Fix adxl34x formating and compatible string

This patch fixes the formating of DTS bindings for the adxl34x digital
accelerometer, and updates the compatible string after the deprecation
of "adxl345x" compatible string.

Signed-off-by: Walter Lozano <walter@vanguardiasur.com.ar>
Acked-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>