net: dsa: bcm_sf2: Remove set but not used variables 'v6_spec, v6_m_spec'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/dsa/bcm_sf2_cfp.c: In function 'bcm_sf2_cfp_ipv6_rule_set':
drivers/net/dsa/bcm_sf2_cfp.c:606:40: warning:
 variable 'v6_m_spec' set but not used [-Wunused-but-set-variable]
drivers/net/dsa/bcm_sf2_cfp.c:606:30: warning:
 variable 'v6_spec' set but not used [-Wunused-but-set-variable]

It not used any more after commit e4f7ef54

 ("dsa: bcm_sf2: use flow_rule
infrastructure")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>