ath9k: Identify baseband watchdog signatures

A full HW reset is not required for all baseband watchdog
signatures. Some BB watchdog updates are benign and can
be discarded, some require re-programming of certain registers
and others require a chip reset.

This patch adds a routine to identify such signatures.

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