staging: rtl8188eu: Remove struct evt_priv and its uses

c2h_wk (work_struct) is naver scheduled to handle events,
so no use of keeping event data.
And also function rtw_hal_c2h_handler() responsible for handling c2h events,
is a dummy function.

Signed-off-by: navin patidar <navin.patidar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>