usb: dwc3: Workaround for irq mask issue

This is a workaround for STAR 9000961433 which affects only version
3.00a of the DWC_usb3 core. This prevents the controller interrupt from
being masked while handling events. Enabling interrupt moderation allows
us to work around this issue because once the GEVNTCOUNT.count is
written the IRQ is immediately deasserted and won't be asserted again
until GEVNTCOUNT.EHB is cleared.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>