usb: gadget: ss_ep_in_comp_desc can be static

drivers/usb/gadget/legacy/printer.c:222:34: sparse: symbol 'ss_ep_in_comp_desc' was not declared. Should it be static?
drivers/usb/gadget/legacy/printer.c:234:34: sparse: symbol 'ss_ep_out_comp_desc' was not declared. Should it be static?

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