ram: rockchip: rename sdram_common.c/h to sdram.c

rename sdram_common.c in arch/arm/mach-rockchip to sdram.c;
so that we can use the file name sdram_common.c in dram driver for
better understand the code;
clean the related file who has use the header file at the same time.

Signed-off-by: YouMin Chen <cym@rock-chips.com>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/mach-rockchip/Makefile b/arch/arm/mach-rockchip/Makefile
index 45d9b06..a9563ad 100644
--- a/arch/arm/mach-rockchip/Makefile
+++ b/arch/arm/mach-rockchip/Makefile
@@ -25,7 +25,7 @@
 obj-$(CONFIG_MISC_INIT_R) += misc.o
 endif
 
-obj-$(CONFIG_$(SPL_TPL_)RAM) += sdram_common.o
+obj-$(CONFIG_$(SPL_TPL_)RAM) += sdram.o
 
 obj-$(CONFIG_ROCKCHIP_RK3036) += rk3036/
 obj-$(CONFIG_ROCKCHIP_RK3128) += rk3128/