usb: dwc3: drd: File headers are not doc headers

usb: dwc3: drd: File headers are not doc headers

Demote drd.c's file header to a standard comment block.

Fixes the following W=1 build warnings:

 drivers/usb/dwc3/drd.c:20: warning: Function parameter or member 'dwc' not described in 'dwc3_otg_disable_events'
 drivers/usb/dwc3/drd.c:20: warning: Function parameter or member 'disable_mask' not described in 'dwc3_otg_disable_events'

Cc: Felipe Balbi <balbi@kernel.org>
Cc: Roger Quadros <rogerq@ti.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20200702144625.2533530-6-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>