kernel/sched: Force inlining of some routines within the scheduler guts

GCC 6.2.0 is making frustratingly poor inlining decisions with some of
these routines, resulting in an awful lot of runtime calls for code
that is only ever expanded once or twice within the file.

Treat with targetted ALWAYS_INLINE's to force the issue.  The
scheduler code is a hot path.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
2 files changed