usb: gadget: USB_MV_UDC should depend on HAS_DMA

If NO_DMA=y:

drivers/built-in.o: In function `done':
drivers/usb/gadget/mv_udc_core.c:239: undefined reference to `dma_pool_free'
drivers/built-in.o: In function `build_dtd':
drivers/usb/gadget/mv_udc_core.c:371: undefined reference to `dma_pool_alloc'
drivers/built-in.o: In function `udc_prime_status':
drivers/usb/gadget/mv_udc_core.c:1465: undefined reference to `dma_map_single'
drivers/built-in.o: In function `mv_udc_remove':
drivers/usb/gadget/mv_udc_core.c:2087: undefined reference to `dma_pool_destroy'
drivers/usb/gadget/mv_udc_core.c:2090: undefined reference to `dma_free_coherent'
drivers/built-in.o: In function `mv_udc_probe':
drivers/usb/gadget/mv_udc_core.c:2190: undefined reference to `dma_alloc_coherent'
drivers/usb/gadget/mv_udc_core.c:2201: undefined reference to `dma_pool_create'
drivers/usb/gadget/mv_udc_core.c:2315: undefined reference to `dma_pool_destroy'
drivers/usb/gadget/mv_udc_core.c:2317: undefined reference to `dma_free_coherent'

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>