arm: zynq: Try to enable the first watchdog via aliases

arm: zynq: Try to enable the first watchdog via aliases

The same change as was done for zynqmp with this description:

Add support for enabling the first watchdog pointed via aliases.

DT fragment:
	aliases {
		...
		watchdog0= &watchdog0;
		watchdog1 = &watchdog_lpd;
		...
	};

<zynqmp example removed>

Till this patch the first watchdog found in DT was used and started
which is not enabling all possible configuration based on user request.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>