If NO_DMA=y:

    drivers/built-in.o: In function `txstate':
    musb_gadget.c:(.text+0x35955a): undefined reference to `dma_unmap_single'
    musb_gadget.c:(.text+0x35957e): undefined reference to `dma_sync_single_for_cpu'
    drivers/built-in.o: In function `musb_g_giveback':
    (.text+0x359672): undefined reference to `dma_mapping_error'
    drivers/built-in.o: In function `musb_g_giveback':
    (.text+0x3596ba): undefined reference to `dma_unmap_single'
    drivers/built-in.o: In function `musb_g_giveback':
    (.text+0x3596e0): undefined reference to `dma_sync_single_for_cpu'
    drivers/built-in.o: In function `rxstate':
    musb_gadget.c:(.text+0x3599d0): undefined reference to `dma_unmap_single'
    musb_gadget.c:(.text+0x3599f6): undefined reference to `dma_sync_single_for_cpu'
    drivers/built-in.o: In function `musb_gadget_queue':
    musb_gadget.c:(.text+0x35a8c0): undefined reference to `dma_map_single'
    musb_gadget.c:(.text+0x35a8d0): undefined reference to `dma_mapping_error'
    musb_gadget.c:(.text+0x35a906): undefined reference to `dma_sync_single_for_cpu'
    musb_gadget.c:(.text+0x35a9a0): undefined reference to `dma_unmap_single'
    musb_gadget.c:(.text+0x35a9c8): undefined reference to `dma_sync_single_for_cpu'
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>