ath9k: Fix QuickDrop usage

commit 93c1cfbe598f72cfa7be49e4a7d2a1d482e15119 upstream.

Bit 5 in the miscConfiguration field of the base EEPROM
header denotes whether QuickDrop is enabled or not. Fix
the incorrect usage of BIT(1) and also make sure that
this is done only for the required chips.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>