This driver currently doesn't support any control flags.

Use flow_rule_has_control_flags() to check for control flags,
such as can be set through `tc flower ... ip_flags frag`.

In case any control flags are masked, flow_rule_has_control_flags()
sets a NL extended error message, and we return -EOPNOTSUPP.

Only compile-tested.
Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240418161821.189263-1-ast@fiberby.netSigned-off-by: Jakub Kicinski <kuba@kernel.org>