drivers: sensor: kconfig: Explicitly add default trigger mode as none

Explicitly add default trigger mode as none in the kconfig trigger
template for better readability.

Signed-off-by: Mayank Narang <[email protected]>

Author: narangmayank

drivers/sensor/Kconfig.trigger_template

@@ -4,6 +4,7 @@
 
 choice "$(module)_TRIGGER_MODE"
 	prompt "Trigger mode"
+	default $(module)_TRIGGER_NONE
 	help
 	  Specify the type of triggering to be used by the sensor module.