vrf: Remove unnecessary NULL check

vrf: Remove unnecessary NULL check

The VRF driver always allocates an IPv4 dst entry for a VRF device and
prevents the device from being registered if the allocation fails.

Therefore, there is no need to check if the entry exists when tearing
down a VRF device. Remove the check.

Note that the same is not true for the IPv6 dst entry. Its creation can
be skipped if IPv6 is administratively disabled (i.e.,
'ipv6.disable=1').

Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260326203233.1128554-2-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>