net: emaclite: Remove custom BUFFER_ALIGN macro

BUFFER_ALIGN macro is used to calculate the number of bytes
required for the next alignment. Instead of this, we can directly
use the skb_reserve(skb, NET_IP_ALIGN) to make the protocol header
buffer aligned on at least a 4-byte boundary, where the NET_IP_ALIGN
is by default defined as 2. So removing the BUFFER_ALIGN and its
related defines which it can be done by the skb_reserve() itself.

Signed-off-by: Shravya Kumbham <shravya.kumbham@xilinx.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>