net/iavf: fix flow access

net/iavf: fix flow access

Add invalid flow checking func in iavf generic flow to avoid the error
of "Cannot access memory at address 0xXXXXXX" occur.

When hash init, the default RSS rules would be added, while hash uninit,
the default RSS rules should be deleted. Add the missing part in the
hash uninit process.

Fixes: 5ea614254332 ("net/iavf: fix VF reset for RSS")
Fixes: ff2d0c345c3b ("net/iavf: support generic flow API")

Signed-off-by: Jeff Guo <jia.guo@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>
Tested-by: Yuan Peng <yuan.peng@intel.com>