sh: Zero-out coherent buffer in consistent_alloc().

Be sure to zero out the buffer, this was causing occasional problems
under heavier PCI tests.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/mm/consistent.c b/arch/sh/mm/consistent.c
index c81e6b6..38c82d8 100644
--- a/arch/sh/mm/consistent.c
+++ b/arch/sh/mm/consistent.c
@@ -28,6 +28,7 @@
 	split_page(page, order);
 
 	ret = page_address(page);
+	memset(ret, 0, size);
 	*handle = virt_to_phys(ret);
 
 	/*