usb: gadget: udc: core: Use pr_fmt() to prefix messages

Instead of duplicating, use pr_fmt() to prefix pr_*() messages.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20211004144126.49154-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>