wil6210: fix name of tracing config option

Tracing in wil6210 is activated with WIL6210_TRACING and not with
ATH6KL_TRACING, this is used for the ath6kl driver. Rename the config
option.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>