MIPS: Don't unmap the memory for dma_sync*.

We were getting away with this for so long only because the only platform
with a non-empty plat_unmap_dma_mem() doesn't call dma_sync_sg_for_cpu()
and dma_sync_sg_for_device() from its commonly used drivers.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
index 891312f..5b98d0e 100644
--- a/arch/mips/mm/dma-default.c
+++ b/arch/mips/mm/dma-default.c
@@ -324,7 +324,6 @@
 		if (cpu_is_noncoherent_r10000(dev))
 			__dma_sync((unsigned long)page_address(sg_page(sg)),
 			           sg->length, direction);
-		plat_unmap_dma_mem(sg->dma_address);
 	}
 }
 
@@ -342,7 +341,6 @@
 		if (!plat_device_is_coherent(dev))
 			__dma_sync((unsigned long)page_address(sg_page(sg)),
 			           sg->length, direction);
-		plat_unmap_dma_mem(sg->dma_address);
 	}
 }