zbus: separate clang-format control comments

Add a line of whitespace between `/* clang-format off */` comments and
the first line of doxygen comment blocks. Some intellisense parsers
will combine all sequential comment blocks when providing code context.
This results in the control comment appearing in the help text for
`ZBUS_CHAN_DEFINE`, for example.

Signed-off-by: Jordan Yates <[email protected]>

include/zephyr/zbus/zbus.h

@@ -259,6 +259,7 @@ struct zbus_channel_observation {
 /** @endcond */
 
 /* clang-format off */
+
 /**
  * @brief Add a static channel observervation.
  *
@@ -321,6 +322,7 @@ struct zbus_channel_observation {
 #define ZBUS_OBSERVERS(...) __VA_ARGS__
 
 /* clang-format off */
+
 /**
  * @brief Zbus channel definition.
  *
@@ -383,6 +385,7 @@ struct zbus_channel_observation {
 	}
 
 /* clang-format off */
+
 /**
  * @brief Define and initialize a subscriber.
  *
@@ -428,6 +431,7 @@ struct zbus_channel_observation {
 	ZBUS_SUBSCRIBER_DEFINE_WITH_ENABLE(_name, _queue_size, true)
 
 /* clang-format off */
+
 /**
  * @brief Define and initialize a listener.
  *
@@ -467,6 +471,7 @@ struct zbus_channel_observation {
 #define ZBUS_LISTENER_DEFINE(_name, _cb) ZBUS_LISTENER_DEFINE_WITH_ENABLE(_name, _cb, true)
 
 /* clang-format off */
+
 /**
  * @brief Define and initialize a message subscriber.
  *