net: dsa: rtl8366: Fix a bug in deleting VLANs

We were checking that the MC (member config) was != 0
for some reason, all we need to check is that the config
has no ports, i.e. no members. Then it can be recycled.
This must be some misunderstanding.

Fixes: 4ddcaf1e ("net: dsa: rtl8366: Properly clear member config")
Cc: Mauri Sandberg <sandberg@mailfence.com>
Cc: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>