[PATCH] ppc32: Added support for the Book-E style Watchdog Timer

PowerPC 40x and Book-E processors support a watchdog timer at the processor
core level.  The timer has implementation dependent timeout frequencies
that can be configured by software.

One the first Watchdog timeout we get a critical exception.  It is left to
board specific code to determine what should happen at this point.  If
nothing is done and another timeout period expires the processor may
attempt to reset the machine.

Command line parameters:
  wdt=0 : disable watchdog (default)
  wdt=1 : enable watchdog

  wdt_period=N : N sets the value of the Watchdog Timer Period.

  The Watchdog Timer Period meaning is implementation specific. Check
  User Manual for the processor for more details.

This patch is based off of work done by Takeharu Kato.

Signed-off-by: Matt McClintock <msm@freescale.com>
Signed-off-by: Kumar Gala <kumar.gala@freescale.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>