dmaengine: Move dma_get_{,any_}slave_channel() to private dmaengine.h

The functions dma_get_slave_channel() and dma_get_any_slave_channel()
are called from DMA engine drivers only.  Hence move their declarations
from the public header file <linux/dmaengine.h> to the private header
file drivers/dma/dmaengine.h.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200121093311.28639-4-geert+renesas@glider.beSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/dmaengine.h

@@ -179,4 +179,7 @@ dmaengine_desc_callback_valid(struct dmaengine_desc_callback *cb)
 	return (cb->callback) ? true : false;
 }
 
+struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
+struct dma_chan *dma_get_any_slave_channel(struct dma_device *device);
+
 #endif

drivers/dma/of-dma.c

@@ -15,6 +15,8 @@
 #include <linux/of.h>
 #include <linux/of_dma.h>
 
+#include "dmaengine.h"
+
 static LIST_HEAD(of_dma_list);
 static DEFINE_MUTEX(of_dma_lock);
 

include/linux/dmaengine.h

@@ -1522,8 +1522,6 @@ int dma_async_device_register(struct dma_device *device);
 int dmaenginem_async_device_register(struct dma_device *device);
 void dma_async_device_unregister(struct dma_device *device);
 void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
-struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
-struct dma_chan *dma_get_any_slave_channel(struct dma_device *device);
 #define dma_request_channel(mask, x, y) \
 	__dma_request_channel(&(mask), x, y, NULL)