ddr: Migrate DDR_SPD to Kconfig

Move the symbol that controls building some JEDEC SPD support functions
to Kconfig.  This is required on the TI keystone 2 platforms and very
frequently (but not always) used on large number of Freescale/NXP
platforms, so use imply there.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/ddr/fsl/Kconfig b/drivers/ddr/fsl/Kconfig
index 8246f62..6461a54 100644
--- a/drivers/ddr/fsl/Kconfig
+++ b/drivers/ddr/fsl/Kconfig
@@ -116,22 +116,26 @@
 config SYS_FSL_DDR4
 	bool "Freescale DDR4 controller"
 	depends on SYS_FSL_HAS_DDR4
+	imply DDR_SPD
 	select SYS_FSL_DDRC_GEN4
 
 config SYS_FSL_DDR3
 	bool "Freescale DDR3 controller"
 	depends on SYS_FSL_HAS_DDR3
+	imply DDR_SPD
 	select SYS_FSL_DDRC_GEN3 if PPC
 	select SYS_FSL_DDRC_ARM_GEN3 if ARM
 
 config SYS_FSL_DDR2
 	bool "Freescale DDR2 controller"
 	depends on SYS_FSL_HAS_DDR2
+	imply DDR_SPD
 	select SYS_FSL_DDRC_GEN2 if (!MPC86xx && !SYS_FSL_DDRC_GEN3)
 
 config SYS_FSL_DDR1
 	bool "Freescale DDR1 controller"
 	depends on SYS_FSL_HAS_DDR1
+	imply DDR_SPD
 	select SYS_FSL_DDRC_GEN1
 
 endchoice