usb: dwc3: USB_DWC3 should depend on HAS_DMA

If NO_DMA=y:

drivers/built-in.o: In function `dwc3_free_one_event_buffer':
drivers/usb/dwc3/core.c:132: undefined reference to `dma_free_coherent'
drivers/built-in.o: In function `dwc3_alloc_one_event_buffer':
drivers/usb/dwc3/core.c:154: undefined reference to `dma_alloc_coherent'
drivers/built-in.o: In function `dma_set_coherent_mask':
include/linux/dma-mapping.h:93: undefined reference to `dma_supported'
drivers/built-in.o: In function `dwc3_free_trb_pool':
drivers/usb/dwc3/gadget.c:407: undefined reference to `dma_free_coherent'
drivers/built-in.o: In function `dwc3_gadget_exit':
drivers/usb/dwc3/gadget.c:2693: undefined reference to `dma_free_coherent'
drivers/built-in.o: In function `dwc3_alloc_trb_pool':
drivers/usb/dwc3/gadget.c:391: undefined reference to `dma_alloc_coherent'
drivers/built-in.o: In function `dwc3_gadget_init':
drivers/usb/dwc3/gadget.c:2598: undefined reference to `dma_alloc_coherent'
drivers/usb/dwc3/gadget.c:2667: undefined reference to `dma_free_coherent'
drivers/usb/dwc3/gadget.c:2674: undefined reference to `dma_free_coherent'
drivers/usb/dwc3/gadget.c:2678: undefined reference to `dma_free_coherent'

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