Previously, if request_irq() failed, ks_add_pcie_port() always returned
zero (success).  Return the request_irq() failure result instead.

[bhelgaas: changelog]
Signed-off-by: NWei Yongjun <weiyj.lk@gmail.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-By: NMurali Karicheri <m-karicheri2@ti.com>