usb: dwc2: Extract register definitions to common header file

usb: dwc2: Extract register definitions to common header file

The same registers are accessed in both the otg and gatet drivers of
dwc2, and these registers are repeatedly defined in these two parts.
Extract register definitions into a common header file to reduce
redundancy and make the code more maintainable.

Signed-off-by: Kongyang Liu <seashell11234455@gmail.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Tested-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Signed-off-by: Junhui Liu <junhui.liu@pigmoral.tech>
Link: https://lore.kernel.org/r/20250110-dwc2-dev-v4-1-987f4fd6f8b2@pigmoral.tech
Signed-off-by: Mattijs Korpershoek <mkorpershoek@kernel.org>