evb64260: fix "cast to pointer from integer of different size" warnings

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/board/evb64260/zuma_pbb_mbox.c b/board/evb64260/zuma_pbb_mbox.c
index 6f5df6e..8e38102 100644
--- a/board/evb64260/zuma_pbb_mbox.c
+++ b/board/evb64260/zuma_pbb_mbox.c
@@ -165,7 +165,9 @@
 
   pci_read_config_dword(zuma_mbox_dev.dev, PCI_BASE_ADDRESS_0, &iobase);
 
-  zuma_mbox_dev.sip = (PBB_DMA_REG_MAP *) (iobase & PCI_BASE_ADDRESS_MEM_MASK);
+  iobase &= PCI_BASE_ADDRESS_MEM_MASK;
+
+  zuma_mbox_dev.sip = (PBB_DMA_REG_MAP *)iobase;
 
   zuma_mbox_dev.sip->int_mask.word=0;