[WATCHDOG] mpc5200 watchdog (GPT0)

Driver for internal mpc5200 watchdog on general purpose timer 0.
For IPB clock of 132 MHz the maximum timeout is about 32 seconds.

Signed-off-by: Domen Puncer <domen.puncer@telargo.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>