time: faster Nanoseconds call

runtime knows how to get the time of day
without allocating memory.

R=golang-dev, dsymonds, dave, hectorchu, r, cw
CC=golang-dev
https://golang.org/cl/5297078
diff --git a/src/pkg/runtime/linux/arm/sys.s b/src/pkg/runtime/linux/arm/sys.s
index 764e779..45da858 100644
--- a/src/pkg/runtime/linux/arm/sys.s
+++ b/src/pkg/runtime/linux/arm/sys.s
@@ -127,14 +127,14 @@
 	SWI	$0
 	RET
 
-TEXT runtimeĀ·gettime(SB),7,$32
+// int64 nanotime(void) so really
+// void nanotime(int64 *nsec)
+TEXT runtimeĀ·nanotime(SB),7,$32
 	/* dummy version - return 0,0 */
 	MOVW	$0, R1
 	MOVW	0(FP), R0
 	MOVW	R1, 0(R0)
 	MOVW	R1, 4(R0)
-	MOVW	4(FP), R0
-	MOVW	R1, 0(R0)
 
 /*
 	attempt at real version - seg faults