watchdog: xilinx: Remove no_timeout variable

Remove no_timeout variable and check variables
directly.

Suggested-by: Rob Herring <robherring2@gmail.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>