watchdog: imgpdc: Fix default heartbeat

watchdog: imgpdc: Fix default heartbeat

The IMG PDC watchdog driver heartbeat module parameter has no default so
it is initialised to zero. This results in the following warning during
probe:

imgpdc-wdt 2006000.wdt: Initial timeout out of range! setting max timeout

The module parameter description implies that the default value should
be PDC_WDT_DEF_TIMEOUT, which isn't yet used, so initialise it to that.

Also tweak the heartbeat module parameter description for consistency.

Fixes: 93937669e9b5 ("watchdog: ImgTec PDC Watchdog Timer Driver")
Signed-off-by: James Hogan <[email protected]>
Cc: Ezequiel Garcia <[email protected]>
Cc: Naidu Tellapati <[email protected]>
Cc: Jude Abraham <[email protected]>
Cc: [email protected]
Reviewed-by: Guenter Roeck <[email protected]>
Signed-off-by: Wim Van Sebroeck <[email protected]>