l2: fix vrrp prefix mac comparison
l2: fix vrrp prefix mac comparison

VRRP prefix length is 5 bytes, doesn't make sense
to compare with 6 bytes mac address

Type: fix

Signed-off-by: Tianyu Li <1c599f4cedabb0c78bbfcbf824f5988c7b6a2be4@arm.com>
Change-Id: I70a9c9ca769f34a81cd568f9e6b9a3538e6ec710

chrisy/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp