ath5k: fix beacon_int handling

ath5k: fix beacon_int handling

3d5e731bceab2de11ae8ec5ed47aa84f049d5a84
(ath5k: remove conf->beacon_int usage)
removed bintval setting from ath5k_config. We need to init the
interval earlier and don't touch it in add_interface anymore.

Otherwise it will be set only once by upper layer through
bss_info_changed but not on second and further hostap executions.

We ended up having bintval 1000 which rendered the AP useless on
many clients.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Nick Kossifidis <mickflemm@gmail.com>
Cc: Luis R. Rodriguez <lrodriguez@atheros.com>
Cc: Bob Copeland <me@bobcopeland.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>