usb: gadget: udc: remove unused usbf_ep_dma_reg_clrset function

clang with W=1 reports
drivers/usb/gadget/udc/renesas_usbf.c:548:20: error: unused function
  'usbf_ep_dma_reg_clrset' [-Werror,-Wunused-function]
static inline void usbf_ep_dma_reg_clrset(struct usbf_ep *ep, uint offset,
                   ^
This function is not used, so remove it.

Signed-off-by: Tom Rix <trix@redhat.com>
Acked-by: Herve Codina <herve.codina@bootlin.com>
Link: https://lore.kernel.org/r/20230319155910.1706294-1-trix@redhat.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>