wext: Emit event stream entries correctly when compat.

Three major portions to this change:

1) Add IW_EV_COMPAT_LCP_LEN, IW_EV_COMPAT_POINT_OFF,
   and IW_EV_COMPAT_POINT_LEN helper defines.

2) Delete iw_stream_check_add_*(), they are unused.

3) Add iw_request_info argument to iwe_stream_add_*(), and use it to
   size the event and pointer lengths correctly depending upon whether
   IW_REQUEST_FLAG_COMPAT is set or not.

4) The mechanical transformations to the drivers and wireless stack
   bits to get the iw_request_info passed down into the routines
   modified in #3.  Also, explicit references to IW_EV_LCP_LEN are
   replaced with iwe_stream_lcp_len(info).

With a lot of help and bug fixes from Masakazu Mokuno.

Signed-off-by: David S. Miller <davem@davemloft.net>