usb: gadget: udc: core: Fix a bunch of kerneldoc misdemeanours

usb: gadget: udc: core: Fix a bunch of kerneldoc misdemeanours

Firstly, file headers should not be in kerneldoc format.  Function
args should be in the format '@.*: '.  We also take the time to
add some descriptions for various argument which have been
previously left out.  Finally we remove descriptions for absent
arguments.

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

 drivers/usb/gadget/udc/core.c:25: warning: Incorrect use of kernel-doc format:  * struct usb_udc - describes one usb device controller
 drivers/usb/gadget/udc/core.c:36: warning: cannot understand function prototype: 'struct usb_udc '
 drivers/usb/gadget/udc/core.c:901: warning: Function parameter or member 'ep' not described in 'usb_gadget_giveback_request'
 drivers/usb/gadget/udc/core.c:901: warning: Function parameter or member 'req' not described in 'usb_gadget_giveback_request'
 drivers/usb/gadget/udc/core.c:1098: warning: Function parameter or member 'udc' not described in 'usb_gadget_udc_stop'
 drivers/usb/gadget/udc/core.c:1098: warning: Excess function parameter 'gadget' description in 'usb_gadget_udc_stop'
 drivers/usb/gadget/udc/core.c:1098: warning: Excess function parameter 'driver' description in 'usb_gadget_udc_stop'

Cc: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20200703174148.2749969-9-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>