usb: cdns3: cdns3-ep0: Fix a few kernel-doc formatting issues

usb: cdns3: cdns3-ep0: Fix a few kernel-doc formatting issues

Fixes the following W=1 kernel build warning(s):

 drivers/usb/cdns3/cdns3-ep0.c:680: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/usb/cdns3/cdns3-ep0.c:775: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 drivers/usb/cdns3/cdns3-ep0.c:868: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst

Cc: Peter Chen <peter.chen@kernel.org>
Cc: Pawel Laszczak <pawell@cadence.com>
Cc: Roger Quadros <rogerq@kernel.org>
Cc: Aswath Govindraju <a-govindraju@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Pawel Jez <pjez@cadence.com>
Cc: linux-usb@vger.kernel.org
Acked-by: Peter Chen <peter.chen@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210526130037.856068-10-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>