usb: dwc3: dwc3-omap: Fix disable IRQ

In the wrapper the IRQ disable should be done by writing 1's to the
IRQ*_CLR register. Existing code is broken because it instead writes
zeros to IRQ*_SET register.

Fix this by adding functions dwc3_omap_write_irqmisc_clr() and
dwc3_omap_write_irq0_clr() which do the right thing.

Fixes: 72246da4 ("usb: Introduce DesignWare USB3 DRD Driver")
Cc: <stable@vger.kernel.org> # v3.2+
Signed-off-by: George Cherian <george.cherian@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>