PCI hotplug: cpcihp: fix debug module parameter to be bool

Fix debug variable from module parameter to be really bool to
fix 'warning: return from incompatible pointer type'.

Acked-by: Scott Murray <scott@spiteful.org>
Signed-off-by: Danny Kukawka <danny.kukawka@bisect.de>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>