sh: Fix a sign extension bug in memset().

Minor sign-extension bug in SH-specific memset()..

Signed-off-by: Toshinobu Sugioka <sugioka@itonet.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/lib/memset.S b/arch/sh/lib/memset.S
index 9567009..af91fe2 100644
--- a/arch/sh/lib/memset.S
+++ b/arch/sh/lib/memset.S
@@ -29,6 +29,7 @@
 	bf/s	1b
 	 mov.b	r5,@-r4
 2:				! make VVVV
+	extu.b	r5,r5
 	swap.b	r5,r0		!   V0
 	or	r0,r5		!   VV
 	swap.w	r5,r0		! VV00