i40e: fix check of descriptor done flag

i40e: fix check of descriptor done flag

If a descriptor the device drive is handling is the context descriptor,
its type value will be 0x1.
When using the not operator ! to do the conditional check, if the expression
value is zero, the device driver will consider the transaction for this
descriptor has been completed, even its DD field is still 0x1 which means
NIC has not finished the operation on this descriptor.
Use the 0xF to check the DD status to avoid the above issue happens.

Fixes: 4861cde46116 ("i40e: new poll mode driver")
Fixes: 05999aab4ca6 ("i40e: add or delete flow director")

Signed-off-by: Zhe Tao <zhe.tao@intel.com>
Acked-by: Jingjing Wu <jingjing.wu@intel.com>