This patch adds support to detect fw error condition by sending
periodic message (heart beat challenge) to firmware. Upon reception
of the message, fw would send a response event to driver. When
there are no reponses from fw for about 5 cmd driver would
trigger the recovery logic assuming that fw has gone into an
error state.

Capable fw will advertise this capability through
ATH6KL_FW_CAPABILITY_HEART_BEAT_POLL bit. This feature
is disabled by default, can be enabled through a modparam
(heart_beat_poll). This modparam also confiures the polling
interval in msecs.
Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>