sched: Add 'flags' argument to sched_{set,get}attr() syscalls

sched: Add 'flags' argument to sched_{set,get}attr() syscalls

Because of a recent syscall design debate; its deemed appropriate for
each syscall to have a flags argument for future extension; without
immediately requiring new syscalls.

Cc: [email protected]
Cc: Ingo Molnar <[email protected]>
Suggested-by: Michael Kerrisk <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>