[WATCHDOG] w83697hf/hg WDT driver - patch 10

This is patch 10 in the series of patches that converts
Marcus Junker's w83697hf watchdog driver to Samuel Tardieau's
w83697hf/hg watchdog driver.

This patch contains following changes:
 - check whether the device is really present
   (we *can* probe for the device now).

Signed-off-by: Samuel Tardieu <sam@rfc1149.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>