drivers: staging: android: ion: Kconfig: Let it also depend on HAS_DMA

ION need HAS_DMA (e.g. need DMA_SHARED_BUFFER), so it has to depend on
HAS_DMA, or can not pass compiling with allmodconfig under score which
NO_DMA.  And the related error:

    CC      drivers/staging/android/ion/ion_cma_heap.o
  drivers/staging/android/ion/ion_cma_heap.c: In function 'ion_cma_mmap':
  drivers/staging/android/ion/ion_cma_heap.c:168:2: error: implicit declaration of function 'dma_mmap_coherent' [-Werror=implicit-function-declaration]
    return dma_mmap_coherent(dev, vma, info->cpu_addr, info->handle,
    ^
  cc1: some warnings being treated as errors
  make[4]: *** [drivers/staging/android/ion/ion_cma_heap.o] Error 1
  make[3]: *** [drivers/staging/android/ion] Error 2
  make[2]: *** [drivers/staging/android] Error 2
  make[1]: *** [drivers/staging] Error 2
  make: *** [drivers] Error 2
Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/Kconfig

 menuconfig ION
 	bool "Ion Memory Manager"
-	depends on HAVE_MEMBLOCK
+	depends on HAVE_MEMBLOCK && HAS_DMA
 	select GENERIC_ALLOCATOR
 	select DMA_SHARED_BUFFER
 	---help---