net sched actions: fix module auto-loading

Macro __stringify_1() can stringify a macro argument, however IFE_META_*
are enums, so they never expand, however request_module expects an integer
in IFE module name, so as a result it always fails to auto-load.

Fixes: ef6980b6

 ("introduce IFE action")
Signed-off-by: Roman Mashak <mrv@mojatatu.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>