The provision for extra bytes in each rx buffer was meant for allocators
who cannot guarantee cacheline aligned buffer allocation.

cacheline aligned allocation is guaranteed by alloc_skb so this provision is
not required.

This should save 32*128 = 4k of space.

Tested on DM6446 EVM using NFS root, iperf (TCP) and tftp of a gigabyte of data.
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>