Revert "blk-mq: simplify queue mapping & schedule with each possisble CPU"

Revert "blk-mq: simplify queue mapping & schedule with each possisble CPU"

BugLink: http://bugs.launchpad.net/bugs/1765232
This reverts commit 9403a13fd07ef6a5fff7a69860f419d16641bb60.
This patch was applied as part of the fix for LP #1759723 and is
resulting in IO hangs due to some drivers selecting reply queues
which do not have any online CPU mapped.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Khaled Elmously <khalid.elmously@canonical.com>