All drivers before MT7915 have a limit of 128 WCID entries. Stop relying
on ARRAY_SIZE(dev->mt76.wcid), since it no longer reflects that limit.

Fixes: 49e649c3 ("mt76: adjust wcid size to support new 802.11ax generation")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>