ARM: highbank: fix get_tbclk value to timer rate

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
diff --git a/arch/arm/cpu/armv7/highbank/timer.c b/arch/arm/cpu/armv7/highbank/timer.c
index 81dbb27..d93de1e 100644
--- a/arch/arm/cpu/armv7/highbank/timer.c
+++ b/arch/arm/cpu/armv7/highbank/timer.c
@@ -126,5 +126,5 @@
 
 ulong get_tbclk(void)
 {
-	return CONFIG_SYS_HZ;
+	return SYSTIMER_RATE;
 }