pciehp: remove unnecessary free_irq

This patch fixes the problem that the following error messages is
reported when pciehp driver is rmmoded.

	Trying to free already-free IRQ XX

The cause of this problem is that pciehp driver is doing unknown 2nd
free_irq at driver unloading. This patch removes this unknown 2nd
free_irq call.

Note: The pciehp driver should be adapted to standard device driver
mode.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>