usb: dwc2: Fix shutdown callback in platform

commit 4fdf228c upstream.

To avoid lot of interrupts from dwc2 core, which can be asserted in
specific conditions need to disable interrupts on HW level instead of
disable IRQs on Kernel level, because of IRQ can be shared between
drivers.

Cc: stable@vger.kernel.org
Fixes: a40a0031

 ("usb: dwc2: add shutdown callback to platform variant")
Tested-by: Frank Mori Hess <fmh6jj@gmail.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Frank Mori Hess <fmh6jj@gmail.com>
Signed-off-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>