bnx2x: Unlock VF-PF channel on MAC/VLAN config error

Current code returns upon failure, leaving the VF-PF in an unusable state;
This patch adds the missing release so further commands could pass between
PF and VF.

Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>