driver/ddr/altera: Add DDR driver for Altera's SDRAM controller

This patch enables the SDRAM controller that is used on Altera's SoCFPGA
family. This patch configures the SDRAM controller based on a configuration
file that is generated from the Quartus tool, sdram_config.h.

Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
diff --git a/Makefile b/Makefile
index bb0ba9f..469c770 100644
--- a/Makefile
+++ b/Makefile
@@ -649,6 +649,7 @@
 libs-y += drivers/spi/
 libs-$(CONFIG_FMAN_ENET) += drivers/net/fm/
 libs-$(CONFIG_SYS_FSL_DDR) += drivers/ddr/fsl/
+libs-$(CONFIG_ALTERA_SDRAM) += drivers/ddr/altera/
 libs-y += drivers/serial/
 libs-y += drivers/usb/dwc3/
 libs-y += drivers/usb/emul/