watchdog: omap: clearify device tree documentation

ti,hwmods doesn't belong into the compatible section but is a property
on it's own. Also reformat the section of required properties to match the
usual style of dt binding documents.

Signed-off-by: Uwe Kleine-König <[e-mail]>
Reviewed-by: Felipe Balbi <[e-mail]>
Acked-by: Felipe Balbi <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

Documentation/devicetree/bindings/watchdog/omap-wdt.txt

···
 TI Watchdog Timer (WDT) Controller for OMAP
 
 Required properties:
-compatible:
-- "ti,omap3-wdt" for OMAP3
-- "ti,omap4-wdt" for OMAP4
-- ti,hwmods: Name of the hwmod associated to the WDT
+- compatible : "ti,omap3-wdt" for OMAP3 or "ti,omap4-wdt" for OMAP4
+- ti,hwmods : Name of the hwmod associated to the WDT
 
 Examples: