arm: socfpga: Convert Altera DDR SDRAM driver to use Kconfig

Convert Altera DDR SDRAM driver to use Kconfig method.
Enable ALTERA_SDRAM by default if it is on Gen5 target.
Arria 10 will have different driver.

Signed-off-by: Tien Fong Chee <tien.fong.chee@intel.com>
Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>
diff --git a/arch/arm/mach-socfpga/Kconfig b/arch/arm/mach-socfpga/Kconfig
index 18bb6dc..9bfee04 100644
--- a/arch/arm/mach-socfpga/Kconfig
+++ b/arch/arm/mach-socfpga/Kconfig
@@ -43,6 +43,7 @@
 
 config TARGET_SOCFPGA_GEN5
 	bool
+	select ALTERA_SDRAM
 
 choice
 	prompt "Altera SOCFPGA board select"