atl1c: use napi_alloc_skb

Using napi_alloc_skb in NAPI context avoids enable/disable IRQs, which
increases iperf3 result by a few Mbps. Since napi_alloc_skb() uses
NET_IP_ALIGN, convert other alloc methods to the same padding. Tested
on Intel Core2 and AMD K10 platforms.

Signed-off-by: Sieng Piaw Liew <liew.s.piaw@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>