usb: gadget: uvc: to_uvcg_control_header() can be static

drivers/usb/gadget/function/uvc_configfs.c:46:28: sparse: symbol 'to_uvcg_control_header' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:138:25: sparse: symbol 'uvcg_control_header_type' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:164:6: sparse: symbol 'uvcg_control_header_drop' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:721:20: sparse: symbol 'to_uvcg_format' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:798:30: sparse: symbol 'to_uvcg_streaming_header' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:950:25: sparse: symbol 'uvcg_streaming_header_type' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:976:6: sparse: symbol 'uvcg_streaming_header_drop' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:1020:19: sparse: symbol 'to_uvcg_frame' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:1265:25: sparse: symbol 'uvcg_frame_type' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:1315:6: sparse: symbol 'uvcg_frame_drop' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:1338:26: sparse: symbol 'to_uvcg_uncompressed' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:1548:25: sparse: symbol 'uvcg_uncompressed_type' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:1586:6: sparse: symbol 'uvcg_uncompressed_drop' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:1610:19: sparse: symbol 'to_uvcg_mjpeg' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:1761:25: sparse: symbol 'uvcg_mjpeg_type' was not declared. Should it be static?
drivers/usb/gadget/function/uvc_configfs.c:1793:6: sparse: symbol 'uvcg_mjpeg_drop' was not declared. Should it be static?

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>