net/ixgbe: fix flex bytes flow director rule

net/ixgbe: fix flex bytes flow director rule

When a flexbytes flow director rule is created, the FDIRCTRL.FLEX_OFFSET
register is set, and it keeps its affect even after the flow director
flexbytes rule is destroyed, causing packets to be transferred to the
wrong place.

It is because setting FDIRCTRL shall only be permitted on Flow Director
initialization flow or clearing the Flow Director table according to the
datasheet, otherwise device may behave unexpectedly.

In order to evade this limitation, simulate the Flow Director
initialization flow or clearing the Flow Director table by setting
FDIRCMD.CLEARHT to 0x1B and then clear it back to 0x0B.

Fixes: f35fec63dde1 ("net/ixgbe: enable flex bytes for generic flow API")
Cc: stable@dpdk.org
Signed-off-by: Dapeng Yu <dapengx.yu@intel.com>
Tested-by: Jun W Zhou <junx.w.zhou@intel.com>
Acked-by: Jeff Guo <jia.guo@intel.com>