[POWERPC] Add hand-coded assembly strcmp

We have an assembly version of strncmp for the bootwrapper, but not
for the kernel, so we end up using the C version in the kernel.  This
takes the strncmp code from the bootup and copies it to the kernel
proper, adding two instructions so it copes correctly with len==0.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/lib/string.S b/arch/powerpc/lib/string.S
index c4c622d..49eb1f1 100644
--- a/arch/powerpc/lib/string.S
+++ b/arch/powerpc/lib/string.S
@@ -75,6 +75,20 @@
 	beq	1b
 	blr
 
+_GLOBAL(strncmp)
+	PPC_LCMPI r5,0
+	beqlr
+	mtctr	r5
+	addi	r5,r3,-1
+	addi	r4,r4,-1
+1:	lbzu	r3,1(r5)
+	cmpwi	1,r3,0
+	lbzu	r0,1(r4)
+	subf.	r3,r0,r3
+	beqlr	1
+	bdnzt	eq,1b
+	blr
+
 _GLOBAL(strlen)
 	addi	r4,r3,-1
 1:	lbzu	r0,1(r4)