ARM: imx: fix imx_init_l2cache storage class

This fixes the following compilation error:

  arch/arm/mach-imx/system.c:101:123: error: static declaration of ‘imx_init_l2cache’ follows non-static declaration
  In file included from arch/arm/mach-imx/system.c:32:0:
  arch/arm/mach-imx/common.h:165:13: note: previous declaration of ‘imx_init_l2cache’ was here
  arch/arm/mach-imx/system.c:101:123: warning: ‘imx_init_l2cache’ defined but not used [-Wunused-function]

Signed-off-by: Vincent Stehlé <vincent.stehle@freescale.com>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/system.c

@@ -98,7 +98,7 @@ void __init mxc_arch_reset_init_dt(void)
 }
 
 #ifdef CONFIG_CACHE_L2X0
-static void __init imx_init_l2cache(void)
+void __init imx_init_l2cache(void)
 {
 	void __iomem *l2x0_base;
 	struct device_node *np;