[MIPS] Alchemy: replace ffs() with __ffs()

Fix havoc wrought by commit 56f621c7f6f735311eed3f36858b402013023c18 --
au_ffs() and ffs() are equivalent, that patch should have just replaced one
with another.  Now replace ffs() with __ffs() which returns an unbiased bit
number.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/au1000/common/dbdma.c b/arch/mips/au1000/common/dbdma.c
index 9d6ad43..edf91f4 100644
--- a/arch/mips/au1000/common/dbdma.c
+++ b/arch/mips/au1000/common/dbdma.c
@@ -859,7 +859,7 @@
 
 	intstat = dbdma_gptr->ddma_intstat;
 	au_sync();
-	chan_index = ffs(intstat);
+	chan_index = __ffs(intstat);
 
 	ctp = chan_tab_ptr[chan_index];
 	cp = ctp->chan_ptr;