The skb spare room needs to be expanded for SPI header, footer
and possible padding within the TX path. So announce the necessary
space in order to avoid expensive skb_copy_expand calls.
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>