These are not used outside of this sourcefile, so make them static.

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

 drivers/usb/gadget/udc/lpc32xx_udc.c:1929:6: warning: no previous prototype for ‘udc_send_in_zlp’ [-Wmissing-prototypes]
 1929 | void udc_send_in_zlp(struct lpc32xx_udc *udc, struct lpc32xx_ep *ep)
 | ^~~~~~~~~~~~~~~
 drivers/usb/gadget/udc/lpc32xx_udc.c:1943:6: warning: no previous prototype for ‘udc_handle_eps’ [-Wmissing-prototypes]
 1943 | void udc_handle_eps(struct lpc32xx_udc *udc, struct lpc32xx_ep *ep)
 | ^~~~~~~~~~~~~~

Cc: Felipe Balbi <balbi@kernel.org>
Cc: Sylvain Lemieux <slemieux.tyco@gmail.com>
Cc: Kevin Wells <kevin.wells@nxp.com>
Cc: Roland Stigge <stigge@antcom.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Vladimir Zapolskiy <vz@mleia.com>
Link: https://lore.kernel.org/r/20200706133341.476881-13-lee.jones@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>