watchdog: stmp3xxx: Remove unused variables

Commit 8d2fa171 ("watchdog: stmp3xxx: Stop the watchdog on system
halt") introduced the following build warning:

drivers/watchdog/stmp3xxx_rtc_wdt.c: In function 'wdt_notify_sys':
drivers/watchdog/stmp3xxx_rtc_wdt.c:78:29: warning: unused variable 'pdata' [-Wunused-variable]

Remove the unused 'pdata' and 'dev' variables.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>