dma-mapping: fix ia64 build, use PHYS_PFN

kbuild test robot reports:

   In file included from include/linux/skbuff.h:34:0,
                    from include/linux/tcp.h:21,
                    from drivers/net/ethernet/amd/xgbe/xgbe-drv.c:119:
   include/linux/dma-mapping.h: In function 'dma_map_resource':
>> include/linux/dma-mapping.h:274:22: error: implicit declaration of function '__phys_to_pfn' [-Werror=implicit-function-declaration]
     unsigned long pfn = __phys_to_pfn(phys_addr);
                         ^~~~~~~~~~~~~

ia64 does not provide __phys_to_pfn(), use the PHYS_PFN() alias.
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

include/linux/dma-mapping.h

@@ -271,7 +271,7 @@ static inline dma_addr_t dma_map_resource(struct device *dev,
 					  unsigned long attrs)
 {
 	struct dma_map_ops *ops = get_dma_ops(dev);
-	unsigned long pfn = __phys_to_pfn(phys_addr);
+	unsigned long pfn = PHYS_PFN(phys_addr);
 	dma_addr_t addr;
 
 	BUG_ON(!valid_dma_direction(dir));