usb: dwc3: introduce flatten model driver of i.MX Soc

The i.MX USB glue and DWC3 core are closely coupled. Describe the i.MX
USB block in a single block will bring more benefits than a parent-
child relation. To support the flatten model devicetree, DWC3 USB core
driver already support to directly register and initialize the core in
glue layer using one device. And many notification can be received in
glue layer timely and proper actions can be executed accordingly.

To align with mainstream, introduce a new driver to support flatten dwc3
devicetree model for i.MX Soc. Besides this driver disables wakeup irq
when system is active, no other function change in this version compared
to dwc3-imx8mp.c. After this new driver is settled, only maintenance
fixes will be added to dwc3-imx8mp.c, new features will only be added
to this new driver. Once all users switch to this new one, the legacy
driver will be removed at proper time.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://patch.msgid.link/20260212-add-flatten-dts-based-dwc3-imx-driver-v5-3-ff04a75ce221@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>