USB: musb: musb_gadget: fix sparse warning

Fix the following sparse warnings:

drivers/usb/musb/musb_gadget.c:1161:5: warning: symbol 'musb_gadget_set_halt' was not declared. Should it be static?

drivers/usb/musb/musb_gadget.c:1244:5: warning: symbol 'musb_gadget_set_wedge' was not declared. Should it be static?

Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>