sched: Use macro for magic number of -1 for setparam

Instead of passing around a magic number -1 for the sched_setparam()
policy, use a more descriptive macro name like SETPARAM_POLICY.

[ based on top of Daniel's sched_setparam() fix ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Daniel Bristot de Oliveira<bristot@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140723112826.6ed6cbce@gandalf.local.home
Signed-off-by: Ingo Molnar <mingo@kernel.org>