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/arch/arm/mach-imx/mx6/Kconfig b/arch/arm/mach-imx/mx6/Kconfig
index 8944432..567a6a6 100644
--- a/arch/arm/mach-imx/mx6/Kconfig
+++ b/arch/arm/mach-imx/mx6/Kconfig
@@ -9,7 +9,7 @@
 
 config MX6
 	select ARM_ERRATA_743622 if !MX6UL && !MX6ULL
-	select GPT_TIMER
+	select GPT_TIMER if !MX6UL && !MX6ULL
 	bool
 	default y
 	imply CMD_FUSE
@@ -54,6 +54,7 @@
 	select HAS_CAAM
 	select SYS_L2CACHE_OFF
 	select ROM_UNIFIED_SECTIONS
+	select SYSCOUNTER_TIMER
 	bool
 
 config MX6UL_LITESOM
@@ -76,6 +77,7 @@
 config MX6ULL
 	select SYS_L2CACHE_OFF
 	select ROM_UNIFIED_SECTIONS
+	select SYSCOUNTER_TIMER
 	bool
 
 config MX6_DDRCAL