event: Fix a wrong type_name from dm_post_init to dm_post_init_f

DM_POST_INIT was changed to DM_POST_INIT_F.
To debug correct message, change type_name from dm_post_init to
dm_post_init_f.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
s/an/a/ :
Signed-off-by: Simon Glass <sjg@chromium.org>