idpf: fix memory leak of flow steer list on rmmod

idpf: fix memory leak of flow steer list on rmmod

The flow steering list maintains entries that are added and removed as
ethtool creates and deletes flow steering rules. Module removal with active
entries causes memory leak as the list is not properly cleaned up.

Prevent this by iterating through the remaining entries in the list and
freeing the associated memory during module removal. Add a spinlock
(flow_steer_list_lock) to protect the list access from multiple threads.

Fixes: ada3e24b84a0 ("idpf: add flow steering support")
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Sreedevi Joshi <sreedevi.joshi@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>