usb: dwc2: Clean up with bitfield macros

usb: dwc2: Clean up with bitfield macros

Use FIELD_PREP, FIELD_GET, BIT, and GENMASK macros to standardize bit
manipulation across the DWC2 code, improving readability and
maintainability without altering functionality.

Signed-off-by: Kongyang Liu <seashell11234455@gmail.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Tested-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Junhui Liu <junhui.liu@pigmoral.tech>
Link: https://lore.kernel.org/r/20250110-dwc2-dev-v4-4-987f4fd6f8b2@pigmoral.tech
Signed-off-by: Mattijs Korpershoek <mkorpershoek@kernel.org>