Convert CONFIG_CHIP_SELECTS_PER_CTRL to Kconfig

This converts the following to Kconfig:
   CONFIG_CHIP_SELECTS_PER_CTRL

Cc: Alison Wang <alison.wang@nxp.com>
Cc: Pramod Kumar <pramod.kumar_1@nxp.com>
Cc: Priyanka Jain <priyanka.jain@nxp.com>
Cc: Rajesh Bhagat <rajesh.bhagat@nxp.com>
Cc: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/ddr/fsl/Kconfig b/drivers/ddr/fsl/Kconfig
index b0e6df8..2771670 100644
--- a/drivers/ddr/fsl/Kconfig
+++ b/drivers/ddr/fsl/Kconfig
@@ -49,6 +49,10 @@
 			ARCH_LX2162A
 	default 1
 
+config CHIP_SELECTS_PER_CTRL
+	int "Number of chip selects per controller"
+	default 4
+
 config SYS_FSL_DDR_VER
 	int
 	default 50 if SYS_FSL_DDR_VER_50