net: macb: Clean 64b dma addresses if they are not detected

Clear ADDR64 dma bit in DMACFG register in case that HW_DMA_CAP_64B is
not detected on 64bit system.
The issue was observed when bootloader(u-boot) does not check macb
feature at DCFG6 register (DAW64_OFFSET) and enabling 64bit dma support
by default. Then macb driver is reading DMACFG register back and only
adding 64bit dma configuration but not cleaning it out.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb_main.c

@@ -2160,6 +2160,7 @@ static void macb_configure_dma(struct macb *bp)
  else
  dmacfg &= ~GEM_BIT(TXCOEN);
 
+ dmacfg &= ~GEM_BIT(ADDR64);
 #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
  if (bp->hw_dma_cap & HW_DMA_CAP_64B)
  dmacfg |= GEM_BIT(ADDR64);