vrf: Remove unnecessary RCU-bh critical section

dev_queue_xmit_nit() already uses rcu_read_lock() / rcu_read_unlock()
and nothing suggests that softIRQs should be disabled around it.
Therefore, remove the rcu_read_lock_bh() / rcu_read_unlock_bh()
surrounding it.

Tested using [1] with lockdep enabled.

[1]
#!/bin/bash

ip link add name vrf1 up type vrf table 100
ip link add name veth0 type veth peer name veth1
ip link set dev veth1 master vrf1
ip link set dev veth0 up
ip link set dev veth1 up
ip address add 192.0.2.1/24 dev veth0
ip address add 192.0.2.2/24 dev veth1
ip rule add pref 32765 table local
ip rule del pref 0
tcpdump -i vrf1 -c 20 -w /dev/null &
sleep 10
ping -i 0.1 -c 10 -q 192.0.2.2

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230821142339.1889961-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>