watchdog: imx2_wdt: Use 'dev' instead of dereferencing it repeatedly

Add helper variable dev = &pdev->dev to simply the code.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/1569308828-8320-3-git-send-email-Anson.Huang@nxp.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>