staging: wfx: fix RCU usage in wfx_join_finalize()

staging: wfx: fix RCU usage in wfx_join_finalize()

Access to sta->ht_cap is protected by RCU. However,
hif_set_association_mode() may sleep, so it can't be called in RCU.

This patch fix this behavior by handling sta and its RCU directly from
function hif_set_association_mode().

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Fixes: d00149011066 ("staging: wfx: fix RCU usage")
Link: https://lore.kernel.org/r/20200310101356.182818-5-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>