ixgbe/base: remove wait and check flow director signature addition

ixgbe/base: remove wait and check flow director signature addition

Waiting for FDIRCMD completion is an expensive thing to do in the
transmit hot path. This wait was added to catch problems with perfect
filter rules, and, at least in the Linux driver, there is no error
check anyway, so there is no point to adding the delay. So do not wait
for completion. Change the return of the function to void, since it has
no meaningful return value.

Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>