imx: initialize and use generic timer on i.MX 6UL/ULL

The i.MX 6UL/ULL feature a Cortex-A7 CPU which suppor the ARM
generic timer. This change makes use of the ARM generic timer in
U-Boot.

This is crucial to make the ARM generic timers usable in Linux since
timer_init() initalizes the system counter module, which is necessary
to use the generic timers CP15 registers.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
diff --git a/include/configs/mx6_common.h b/include/configs/mx6_common.h
index 59e6dae..ddc645c 100644
--- a/include/configs/mx6_common.h
+++ b/include/configs/mx6_common.h
@@ -7,7 +7,10 @@
 #ifndef __MX6_COMMON_H
 #define __MX6_COMMON_H
 
-#if !(defined(CONFIG_MX6UL) || defined(CONFIG_MX6ULL))
+#if (defined(CONFIG_MX6UL) || defined(CONFIG_MX6ULL))
+#define CONFIG_SC_TIMER_CLK 8000000 /* 8Mhz */
+#define COUNTER_FREQUENCY CONFIG_SC_TIMER_CLK
+#else
 #ifndef CONFIG_SYS_L2CACHE_OFF
 #define CONFIG_SYS_L2_PL310
 #define CONFIG_SYS_PL310_BASE	L2_PL310_BASE