Clear the irq releated entries in irq_vector, irq_domain and vector_irq
instead of clearing irq_vector only. So when new irq is created, it
could reuse that vector. (actually is the second loop scanning from
FIRST_DEVICE_VECTOR+8). This could avoid the vectors are used up
with enough module inserting and removing

Cc: Eric W. Biedierman <ebiederm@xmission.com>
Cc: Muli Ben-Yehuda <muli@il.ibm.com>
Signed-off-By: Yinghai Lu <yinghai.lu@amd.com>
Signed-off-by: Andi Kleen <ak@suse.de>