ARM: socfpga: Rename the gen5 sdram driver to more specific name

Current sdram driver is only applied to gen5 device, hence it is better
to rename sdram driver to more specific name which is related to gen5
device.

Signed-off-by: Tien Fong Chee <tien.fong.chee@intel.com>
diff --git a/drivers/ddr/altera/Makefile b/drivers/ddr/altera/Makefile
index d42fd44..ec1cb0b 100644
--- a/drivers/ddr/altera/Makefile
+++ b/drivers/ddr/altera/Makefile
@@ -7,5 +7,5 @@
 # Copyright (C) 2014 Altera Corporation <www.altera.com>
 
 ifdef CONFIG_ALTERA_SDRAM
-obj-$(CONFIG_TARGET_SOCFPGA_GEN5) += sdram.o sequencer.o
+obj-$(CONFIG_TARGET_SOCFPGA_GEN5) += sdram_gen5.o sequencer.o
 endif