dmaengine: vdma: Fix compilation warnings

This patch fixes the following compilation warnings.
In file included from drivers/dma/xilinx/xilinx_vdma.c:26:0:
include/linux/dmapool.h:18:4: warning: 'struct device' declared inside parameter list
    size_t size, size_t align, size_t allocation);
    ^
include/linux/dmapool.h:18:4: warning: its scope is only this definition or declaration, which is probably not what you want
include/linux/dmapool.h:31:7: warning: 'struct device' declared inside parameter list
       size_t size, size_t align, size_t allocation);
       ^
drivers/dma/xilinx/xilinx_vdma.c: In function 'xilinx_vdma_alloc_chan_resources':
drivers/dma/xilinx/xilinx_vdma.c:501:20: warning: passing argument 2 of 'dma_pool_create' from incompatible pointer type
  chan->desc_pool = dma_pool_create("xilinx_vdma_desc_pool",
                    ^
In file included from drivers/dma/xilinx/xilinx_vdma.c:26:0:
include/linux/dmapool.h:17:18: note: expected 'struct device *' but argument is of type 'struct device *'
 struct dma_pool *dma_pool_create(const char *name, struct device *dev, .

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

include/linux/dmapool.h

@@ -14,6 +14,8 @@
 #include <asm/io.h>
 #include <asm/scatterlist.h>
 
+struct device;
+
 struct dma_pool *dma_pool_create(const char *name, struct device *dev, 
 			size_t size, size_t align, size_t allocation);