hinic: fix dereference of pointer hwdev before it is null checked

Currently pointer hwdev is dereferenced when assigning hwif before
hwdev is null checked.  Fix this by only derefencing hwdev after the
null check.

Addresses-Coverity: ("Dereference before null check")
Fixes: 4fdc51bb

 ("hinic: add support for rss parameters with ethtool")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>