Revert "usb: host: xhci-plat: Specify IRQF_ONESHOT in irqflag"

This reverts commit 577ec59a.

The dwc3 gadget which shares this IRQ no longer uses IRQF_ONESHOT.
Since all requests sharing the IRQ must have matching flags, also
remove IRQF_ONESHOT from xhci-plat.

Change-Id: Ic15373b5a541cdc19dafd23c4dd2a7a7ada347a4
Signed-off-by: Jack Pham <jackp@codeaurora.org>