bnx2x: make bnx2x_close() static again

Commit 8304859a "bnx2x: add fan failure event handling" made the function
bnx2x_close() non-static unnecessarily. The function is not called from
other sources. Make it static again.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Acked-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>