sched/headers/uapi: Fix linux/sched/types.h userspace compilation errors

Consistently use types provided by <linux/types.h> to fix the following
linux/sched/types.h userspace compilation errors:

  /usr/include/linux/sched/types.h:57:2: error: unknown type name 'u32'
    u32 size;
  ...
  u64 sched_period;

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org # v4.12
Fixes: e2d1e2ae

 ("sched/headers: Move various ABI definitions to <uapi/linux/sched/types.h>")
Link: http://lkml.kernel.org/r/20170705162328.GA11026@altlinux.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>