percpu: make percpu-km set chunk->populated bitmap properly

percpu-km instantiates the whole chunk on creation and doesn't make
use of chunk->populated bitmap and leaves it as zero.  While this
currently doesn't cause any problem, the inconsistency makes it
difficult to build further logic on top of chunk->populated.  This
patch makes percpu-km fill chunk->populated on creation so that the
bitmap is always consistent.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>