PCI hotplug: shpchp: fix bus number check to avoid false positive

With for (busnr = 0; busnr <= end; busnr++) { ... } busnr reaches end + 1
after the loop.  So fix the "no busses available" check to look for just
busnr > end rather than >=.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>