e_comp_wl: Add a hook point for destruction of comp_data

e_comp_wl: Add a hook point for destruction of comp_data

This is to add a hook point, E_COMP_WL_HOOK_DEL which will be triggered
right before comp_data gets destroyed.

Many implementations of E20 have referred to ec->comp_data, but there
have been no way to find out when it's deleted.
So, we have had to check the validation of it before accessing it.

Through this patch, we can now ensure the validation of comp_data by
using a handler of E_COMP_WL_HOOK_DEL.

Change-Id: I7485d9b11a1ea46d500b4b0eac165e8529045cae