dmaengine: of: kconfig: select DMA_ENGINE when DMA_OF is selected

Select DMA_ENGINE when DMA_OF is selected since
of_dma_xlate_by_chan_id() from drivers/dma/of-dma.c uses
dma_get_slave_channel() from drivers/dma/dmaengine.c

This resolves error reported:

drivers/built-in.o: In function `of_dma_xlate_by_chan_id':
drivers/dma/of-dma.c:253: undefined reference to `dma_get_slave_channel'
Signed-off-by: Alexander Popov <a13xp0p0v88@gmail.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/Kconfig

@@ -396,6 +396,7 @@ config DMA_ACPI
 config DMA_OF
 	def_bool y
 	depends on OF
+	select DMA_ENGINE
 
 comment "DMA Clients"
 	depends on DMA_ENGINE