imx: Add get_tbclk() function for imx25

Need this function for autoboot keyd
Signed-off-by: NMatthias Weisser <weisserm@arcor.de>

arch/arm/cpu/arm926ejs/mx25/timer.c

@@ -187,3 +187,15 @@ void __udelay (unsigned long usec)
 	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;
+}