cxgb4vf: fix memleak in mac_hlist initialization

mac_hlist was initialized during adapter_up, which will be called
every time a vf device is first brought up, or every time when device
is brought up again after bringing all devices down. This means our
state of previous list is lost, causing a memleak if entries are
present in the list. To fix that, move list init to the condition
that performs initial one time adapter setup.

Signed-off-by: Arjun Vynipadath <arjun@chelsio.com>
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>