pkt_sched: Include const.h

Commit 9903c8dc changed TC_ETF defines to use _BITUL instead of BIT
but did not add the dependecy on linux/const.h. As a consequence,
importing the uapi headers into iproute2 causes builds to fail. Add
the dependency.

Fixes: 9903c8dc ("etf: Don't use BIT() in UAPI headers.")
Cc: Vedang Patel <vedang.patel@intel.com>
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/uapi/linux/pkt_sched.h

@@ -2,6 +2,7 @@
 #ifndef __LINUX_PKT_SCHED_H
 #define __LINUX_PKT_SCHED_H
 
+#include <linux/const.h>
 #include <linux/types.h>
 
 /* Logical priority bands not depending on specific packet scheduler.