watchdog: pnx4008: don't use __raw_-accessors

__raw_readl/__raw_writel are not meant for drivers [1].

[1] http://thread.gmane.org/gmane.linux.ports.arm.kernel/117626



Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>