usb: dwc3: core: cleanup IRQ resources

Implementations might use different IRQs for
host, gadget so use named interrupt resources
to allow device tree to specify the interrupts.

Following are the interrupt names

Peripheral Interrupt - peripheral
HOST Interrupt - host

Maintain backward compatibility for a single named
interrupt ("dwc3_usb3") for all interrupts as well as
unnamed interrupt at index 0 for all interrupts.

As platform_get_irq() variants are used, tackle
the -EPROBE_DEFER case as well.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>