watchdog: mpc8xxx: Add support for mpc83xx

Introduce a new compatible "fsl,pq2pro-wdt"
On mpc83xx, the prescaling factor is 0x10000.

Don't write the watchdog configuration register in
start.S as it can be written only once.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
4 files changed