i40e: Fix Flow Director raw_buf cleanup

The Tx cleanup flow was incorrectly assuming it could check for the flow
director bits after it had unmapped the buffer.  However in this case it
results in us trying to free a raw_buf as though it is an sk_buff.

To fix this I am moving up the flag test for the FD_SB bit so that when
find a non-NULL skb or raw_buf value we then check the flag and use the
appropriate call to free the buffer.

Change-ID: I6284034ba1ea87c9922e56f6eb3181f7f09bddde
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>