[dev.cc] runtime: fix FP reference in atomic_ppc64x.s

References to FP must now have a symbol.

Change-Id: I3f06b99cc48cbd4ccd6f23f2e4b0830af40f7f3d
Reviewed-on: https://go-review.googlesource.com/5281Reviewed-by: Russ Cox <rsc@golang.org>

src/runtime/atomic_ppc64x.s

@@ -8,7 +8,7 @@
 
 // uint32 runtime·atomicload(uint32 volatile* addr)
 TEXT ·atomicload(SB),NOSPLIT,$-8-12
-	MOVD	0(FP), R3
+	MOVD	addr+0(FP), R3
 	SYNC
 	MOVWZ	0(R3), R3
 	CMPW	R3, R3, CR7
@@ -19,7 +19,7 @@ TEXT ·atomicload(SB),NOSPLIT,$-8-12
 
 // uint64 runtime·atomicload64(uint64 volatile* addr)
 TEXT ·atomicload64(SB),NOSPLIT,$-8-16
-	MOVD	0(FP), R3
+	MOVD	addr+0(FP), R3
 	SYNC
 	MOVD	0(R3), R3
 	CMP	R3, R3, CR7
@@ -30,7 +30,7 @@ TEXT ·atomicload64(SB),NOSPLIT,$-8-16
 
 // void *runtime·atomicloadp(void *volatile *addr)
 TEXT ·atomicloadp(SB),NOSPLIT,$-8-16
-	MOVD	0(FP), R3
+	MOVD	addr+0(FP), R3
 	SYNC
 	MOVD	0(R3), R3
 	CMP	R3, R3, CR7