ath9k: Fix RX filter calculation

If multiple channel contexts are active, then the opmode
can be different in each context. Since the RX filter is
calculated in ath_startrecv() before switching to the
new opmode, the wrong filters are chosen.

Fix this by calling ath9k_calculate_summary_state() before
the RX module is started.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>