usb: dwc2: Update common interrupt handler to call gadget interrupt handler

Make dwc2_handle_common_intr call the gadget interrupt function when operating
in peripheral mode. Remove the spinlock functions in s3c_hsotg_irq as
dwc2_handle_common_intr() already has the spinlocks.

Move the registeration of the IRQ to common code for platform and PCI.

Remove duplicate interrupt conditions that was in gadget, as those are handled
by dwc2 common interrupt handler.

Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>