mac80211: Fix wpa_supplicant config removal ubus call

mac80211: Fix wpa_supplicant config removal ubus call

If mac80211_setup_supplicant() is called with enabled=0 then it should just
destroy the interface and remove the configuration from wpa_supplicant. But
the ubus method call always returned

  Command failed: Method not found

because the actual name of the method is "config_remove".

Fixes: b5516603dd90 ("mac80211: more wifi reconf related fixes")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
[bump PKG_RELEASE]
Signed-off-by: David Bauer <mail@david-bauer.net>