rockchip: use common sdram function

Replace the sdram_init() in board init and rockchip_sdram_size() in
sdram driver for all the Rockchip SoCs which enable CONFIG_RAM.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Make dram_init() in rk3036-board.c conditional on CONFIG_RAM:
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/arch/arm/mach-rockchip/rk3036-board.c b/arch/arm/mach-rockchip/rk3036-board.c
index bf2b268..26ea23b 100644
--- a/arch/arm/mach-rockchip/rk3036-board.c
+++ b/arch/arm/mach-rockchip/rk3036-board.c
@@ -60,12 +60,18 @@
 	return 0;
 }
 
+#if !CONFIG_IS_ENABLED(RAM)
+/*
+ * When CONFIG_RAM is enabled, the dram_init() function is implemented
+ * in sdram_common.c.
+ */
 int dram_init(void)
 {
 	gd->ram_size = sdram_size();
 
 	return 0;
 }
+#endif
 
 #ifndef CONFIG_SYS_DCACHE_OFF
 void enable_caches(void)