misc: acrn_trace: enlarge DEV_PATH_LEN
Now ACRN support platform which CPU numbers are large than 10. So the old value
for DEV_PATH_LEN is not enough (18 is not enough for /dev/acrn_trace_xx).
#define TRACE_FILE_NAME_LEN 32
#define TRACE_FILE_DIR_LEN (TRACE_FILE_NAME_LEN - 3)
#define TRACE_FILE_ROOT "acrntrace/"
-#define DEV_PATH_LEN 18
+#define DEV_PATH_LEN 20
#define TIME_STR_LEN 16
#define CMD_MAX_LEN 48
