sched/topology: Move sd_flag_debug out of linux/sched/topology.h

Defining an array in a header imported all over the place clearly is a daft
idea, that still didn't stop me from doing it.

Leave a declaration of sd_flag_debug in topology.h and move its definition
to sched/debug.c.

Fixes: b6e862f3

 ("sched/topology: Define and assign sched_domain flag metadata")
Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200825133216.9163-1-valentin.schneider@arm.com