watchdog: pnx4008: update logging during power-on

There is no need to add the driver name in the text to display
on the console during the power-on:
pnx4008-watchdog 4003c000.watchdog: PNX4008 Watchdog Timer: heartbeat 19 sec

Signed-off-by: Sylvain Lemieux <slemieux@tycoint.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>