mac80211: convert UniFi Outdoor+ HSR support to OF

Enable support for the Ubiquiti UniFi Outdoor+ RF filter via
device-tree. The old way of using platform data is not required anymore,
as it was only used on the now removed ar71xx target.

Signed-off-by: David Bauer <mail@david-bauer.net>

target/linux/generic/files/include/linux/ath9k_platform.h

@@ -53,8 +53,6 @@ struct ath9k_platform_data {
 	unsigned num_btns;
 	const struct gpio_keys_button *btns;
 	unsigned btn_poll_interval;
-
-	bool ubnt_hsr;
 };
 
 #endif /* _LINUX_ATH9K_PLATFORM_H */