netfilter: bridge: clean up some inconsistent indenting

Eliminate the follow smatch warning:

net/bridge/netfilter/nf_conntrack_bridge.c:385 nf_ct_bridge_confirm()
warn: inconsistent indenting.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Florian Westphal <fw@strlen.de>