watchdog: mx25: use the imx_watchdog driver for mx25

watchdog: mx25: use the imx_watchdog driver for mx25

The existing imx_watchdog driver is compatible with mx25 chipsets.
Add a WDOG1_BASE_ADDR define for the base address and enable the driver
in watchdog's Makefile.

To use the driver, a board must define CONFIG_IMX_WATCHDOG and
CONFIG_HW_WATCHDOG.

This fixes an issue when booting an mx25 chip via usb/serial. In this
case, the boot rom will always enable the watchdog. If u-boot is running
in interactive mode and the watchdog is not serviced, the system is
rebooted when the watchdog expires.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>