b43: remove wrong probe_resp_plcp write

The tkip hw support uncovered a bug in b43_write_probe_resp_template : it is
writing at the wrong shm offset, it is in the B43_SHM_SH_TKIPTSCTTAK
zone. Remove b43_write_probe_resp_template,  b43_write_probe_resp_plcp
and b43_write_probe_resp_plcp because the probe response offload is
currently not supported by mac80211.

Signed-off-by: Gregor Kowski <gregor.kowski@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>