ARM: imx: let L2 initialization be a common function

Move imx6q L2 initialization function imx6q_init_l2cache() into
system.c, and rename it imx_init_l2cache(), so that other platforms
other than imx6q can also use the function.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Dirk Behme <dirk.behme@de.bosch.com>
diff --git a/arch/arm/mach-imx/common.h b/arch/arm/mach-imx/common.h
index cb6c838..b96aff7 100644
--- a/arch/arm/mach-imx/common.h
+++ b/arch/arm/mach-imx/common.h
@@ -161,6 +161,12 @@
 static inline int mx51_neon_fixup(void) { return 0; }
 #endif
 
+#ifdef CONFIG_CACHE_L2X0
+extern void imx_init_l2cache(void);
+#else
+static inline void imx_init_l2cache(void) {}
+#endif
+
 extern struct smp_operations imx_smp_ops;
 
 #endif