Remove unnecessary CONFIG_HOTPLUG_PCI_PCIE_EVENT_MODE.

The CONFIG_HOTPLUG_PCI_PCIE_POLL_EVENT_MODE option is not needed
because polling mechanism can be enabled through 'pciehp_poll_mode'
module option.
Signed-off-by: NKenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: NKristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>