imx: imx7d: add imx-common cpu support for imx7d

Add imx-common cpu support for imx7d SoC
- Update reset_cause for imx7d
- Enable watchdog driver built for imx7d

Signed-off-by: Adrian Alonso <aalonso@freescale.com>
Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
6 files changed