Altera TSE: Correct typecast issue detected by kbuild test robot

This patch addresses a portable pointer arithmetic issue in the
original submission found by the kbuild test robot.

config: make ARCH=i386 allyesconfig

   altera_sgdma.c: In function 'sgdma_txphysaddr':
>> altera_sgdma.c:393:33: warning: cast from
>> pointer to integer of different size [-Wpointer-to-int-cast]
     dma_addr_t offs = (dma_addr_t)((dma_addr_t)desc -
                                    ^
>> altera_sgdma.c:394:5: warning: cast from
>> pointer to integer of different size [-Wpointer-to-int-cast]
        (dma_addr_t)priv->tx_dma_desc);
        ^
   altera_sgdma.c: In function 'sgdma_rxphysaddr':
>> altera_sgdma.c:403:33: warning: cast from
>> pointer to integer of different size [-Wpointer-to-int-cast]
     dma_addr_t offs = (dma_addr_t)((dma_addr_t)desc -
                                    ^
>> altera_sgdma.c:404:5: warning: cast from
>> pointer to integer of different size [-Wpointer-to-int-cast]
        (dma_addr_t)priv->rx_dma_desc);
        ^

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Vince Bridgers <vbridgers2013@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/altera/altera_sgdma.c

@@ -390,9 +390,8 @@ sgdma_txphysaddr(struct altera_tse_private *priv,
 		 struct sgdma_descrip *desc)
 {
 	dma_addr_t paddr = priv->txdescmem_busaddr;
-	dma_addr_t offs = (dma_addr_t)((dma_addr_t)desc -
-				(dma_addr_t)priv->tx_dma_desc);
-	return paddr + offs;
+	uintptr_t offs = (uintptr_t)desc - (uintptr_t)priv->tx_dma_desc;
+	return (dma_addr_t)((uintptr_t)paddr + offs);
 }
 
 static dma_addr_t
@@ -400,9 +399,8 @@ sgdma_rxphysaddr(struct altera_tse_private *priv,
 		 struct sgdma_descrip *desc)
 {
 	dma_addr_t paddr = priv->rxdescmem_busaddr;
-	dma_addr_t offs = (dma_addr_t)((dma_addr_t)desc -
-				(dma_addr_t)priv->rx_dma_desc);
-	return paddr + offs;
+	uintptr_t offs = (uintptr_t)desc - (uintptr_t)priv->rx_dma_desc;
+	return (dma_addr_t)((uintptr_t)paddr + offs);
 }
 
 #define list_remove_head(list, entry, type, member)			\