ath5k: add sysfs files for ANI parameters

/sys/class/ieee80211/phy0/device/ani/ani_mode
/sys/class/ieee80211/phy0/device/ani/noise_immunity_level
/sys/class/ieee80211/phy0/device/ani/spur_level
/sys/class/ieee80211/phy0/device/ani/firstep_level
/sys/class/ieee80211/phy0/device/ani/ofdm_weak_signal_detection
/sys/class/ieee80211/phy0/device/ani/cck_weak_signal_detection
/sys/class/ieee80211/phy0/device/ani/noise_immunity_level_max
/sys/class/ieee80211/phy0/device/ani/spur_level_max
/sys/class/ieee80211/phy0/device/ani/firstep_level_max

sysfs has a lot of symlinks, so you can find the files also in other locations,
like (by PCI ID) /sys/devices/pci0000:00/0000:00:11.0/ani and others.

Signed-off-by: Bruno Randolf <br1@einfach.org>
Acked-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>