rockchip: Don't skip low-level init

At present the low-level init is skipped on rockchip. Among other things
this means that the instruction cache is left disabled. Fix this.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/arm/mach-rockchip/board.c

@@ -45,3 +45,7 @@ void enable_caches(void)
 	dcache_enable();
 }
 #endif
+
+void lowlevel_init(void)
+{
+}

arch/arm/mach-rockchip/rk3288-board-spl.c

@@ -270,3 +270,7 @@ err:
 	/* No way to report error here */
 	hang();
 }
+
+void lowlevel_init(void)
+{
+}

include/configs/rk3288_common.h

@@ -16,7 +16,6 @@
 #define CONFIG_BAUDRATE			115200
 #define CONFIG_SYS_MALLOC_LEN		(32 << 20)
 #define CONFIG_SYS_CBSIZE		1024
-#define CONFIG_SKIP_LOWLEVEL_INIT
 #define CONFIG_SYS_THUMB_BUILD
 #define CONFIG_OF_LIBFDT
 #define CONFIG_DISPLAY_BOARDINFO