[WATCHDOG] timers cleanup

- Use timer macros to set function and data members and to modify
  expiration time.
- Use DEFINE_TIMER for single (platform dependent) watchdog timers and
  do not init them at run-time in these cases.
- del_timer_sync is common in most cases -- we want to wait for timer
  function if it's still running.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Steve Hill <steve@navaho.co.uk>
Cc: Heiko Ronsdorf <hero@ihg.uni-duisburg.de>
Cc: Fernando Fuganti <fuganti@conectiva.com.br>
Cc: Gergely Madarasz <gorgo@itc.hu>
Cc: Ken Hollis <khollis@bitgate.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>