watchdog: fix typo in the comment

Correctly spelled comments make it easier for the reader to understand
the code.

Fix typos:
'hearbeat' -> 'heartbeat',
'retrigggers' -> 'retriggers',
'funtions' -> 'functions',
'Resgister' -> 'Register'.

Signed-off-by: Yan Zhen <yanzhen@vivo.com>
Reviewed-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Link: https://lore.kernel.org/r/20240923075016.2439774-1-yanzhen@vivo.com


Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>