net/mlx5e: Use napi_alloc_skb for RX SKB allocations

Instead of netdev_alloc_skb, we use the napi_alloc_skb function
which is designated to allocate skbuff's for RX in a
channel-specific NAPI instance, and implies the IP packet alignment.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>