ath9k: Fix tx struck state with paprd

ath9k: Fix tx struck state with paprd

commit 9094537c3a9ef9e127e844254a74186735c9a90b upstream.

Paprd needs to be done only on active chains(not for all the chains
that hw can support). The paprd training frames which are sent
for inactive chains would be hanging on the hw queue without
getting transmitted and would make the connection so unstable.
This issue happens only with the hw which supports paprd cal(ar9003).

Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>