tools: acrn-crashlog: refine the configuration structure

1. get string size when parsing configuration.
2. add 'const' for strings got from configuration.

Tracked-On: #1254
Signed-off-by: Liu, Xinwu <xinwu.liu@intel.com>
Reviewed-by: Yonghua Huang <yonghua.huang@intel.com>
Acked-by: Chen Gang <gang.c.chen@intel.com>

tools/acrn-crashlog/acrnprobe/include/event_queue.h

@@ -22,7 +22,7 @@ __extension__
 struct event_t {
 	int watchfd;
 	enum event_type_t event_type;
-	char *channel;
+	const char *channel;
 	void *private;
 
 	TAILQ_ENTRY(event_t) entries;