tracing/events: add missing type info of dynamic arrays

The format file doesn't contain enough information for
__dynamic_array/__string. The type name is missing.

Before:
  # cat format:
  name: irq_handler_entry
  ...
          field:__data_loc name;  offset:16;      size:2;

After:
  # cat format:
  name: irq_handler_entry
  ...
          field:__data_loc char[] name;  offset:16;      size:2;

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4A5E962E.9020900@cn.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>