wl12xx: remove wl1271_tx_update_filters

wl1271_tx_update_filters() is used as some workaround
to open filters while roaming on the same channel.

However, it doesn't handle roaming to a different channel,
and it might also sleep in the tx path, which is a bug.

With the new auth/assoc redesign, roaming is much simpler,
and this function is not needed anymore.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>