[ALPS08675531] xhci: disable irq after suspend

There is a time interval between xhci suspend and mtu3 suspend.
USB host will be powered down until mtu3 suspend. Disable irq to
prevent irq still be triggered after xhci driver suspend.

log:
bus_id:0x401, vio_addr:0x11200024, slave_type:0x2, shift_sta_bit:1
Violation Type: "Power/clock might not enabled"

MTK-Commit-Id: 4631cf6c7418078551f3c68e2b8b8247dbedc54e

CR-Id: ALPS08675531
Feature: usb_ssusb
Signed-off-by: Eddie Hung <eddie.hung@mediatek.com>
Change-Id: I18d021b2bb219f39874c1456bce0c07fdb956e19