This reverts commit 02dae36a.

That commit is bogus in two ways:

1) There's no way dwc3-omap's ->suspend() can cause any effect
	on xhci's ->suspend(). Linux device driver model guarantees
	that a parent's ->suspend() will only be called after all
	children are suspended. dwc3-omap is the parent of the
	parent of xhci.

2) When implementing Deep Sleep states where context is lost,
	USBOTGSS_IRQ0 register, well, looses context so we
	_must_ rewrite it otherwise core IRQs will never be
	reenabled and USB will appear to be dead.

Fixes: 02dae36a

 (usb: dwc3: dwc3-omap: Disable/Enable only
	wrapper interrupts in prepare/complete)
Cc: <stable@vger.kernel.org> # v3.17
Cc: George Cherian <george.cherian@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>