sched/deadline: Don't use dubious signed bitfields

sched/deadline: Don't use dubious signed bitfields

It doesn't cause a run-time bug, but these bitfields should be unsigned.
When it's signed ->dl_throttled is set to either 0 or -1, instead of
0 and 1 as expected.

The sched.h file is included into tons of places so Sparse generates
a flood of warnings like this:

  ./include/linux/sched.h:477:54: error: dubious one-bit signed bitfield

Reported-by: Matthew Wilcox <[email protected]>
Reported-by: Xin Long <[email protected]>
Signed-off-by: Dan Carpenter <[email protected]>
Reviewed-by: Luca Abeni <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: luca abeni <[email protected]>
Link: http://lkml.kernel.org/r/20171013070121.dzcncojuj2f4utij@mwanda
Signed-off-by: Ingo Molnar <[email protected]>