imx: Add get_tbclk() function for imx25

Need this function for autoboot keyd

Signed-off-by: Matthias Weisser <weisserm@arcor.de>
diff --git a/arch/arm/cpu/arm926ejs/mx25/timer.c b/arch/arm/cpu/arm926ejs/mx25/timer.c
index 14f0c2d..7c8a71b 100644
--- a/arch/arm/cpu/arm926ejs/mx25/timer.c
+++ b/arch/arm/cpu/arm926ejs/mx25/timer.c
@@ -187,3 +187,15 @@
 	while (get_ticks() < tmp)	/* loop till event */
 		 /*NOP*/;
 }
+
+/*
+ * This function is derived from PowerPC code (timebase clock frequency).
+ * On ARM it returns the number of timer ticks per second.
+ */
+ulong get_tbclk(void)
+{
+	ulong tbclk;
+
+	tbclk = CONFIG_MX25_CLK32;
+	return tbclk;
+}