dt-bindings: watchdog: convert zii,rave-sp-wdt.txt to yaml format

Convert device binding doc zii,rave-sp-wdt.txt to yaml format.
Additional changes:
- Ref to watchdog.yaml.
- Remove mfd node in example.
- Remove eeprom part in example.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20241010-zii_yaml-v2-4-0ab730607422@nxp.com


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>