fsl_ddr: Move DDR config options to driver Kconfig

Create driver/ddr/fsl/Kconfig and move existing options. Clean up
existing macros.

Signed-off-by: York Sun <york.sun@nxp.com>
[trini: Migrate sbc8641d, xpedite537x and MPC8536DS, run a moveconfig.py -s]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/xpedite537x_defconfig b/configs/xpedite537x_defconfig
index e38e1da..8e86a33 100644
--- a/configs/xpedite537x_defconfig
+++ b/configs/xpedite537x_defconfig
@@ -15,5 +15,6 @@
 CONFIG_CMD_MII=y
 CONFIG_CMD_PING=y
 CONFIG_CMD_SNTP=y
+CONFIG_SYS_FSL_DDR2=y
 CONFIG_SYS_NS16550=y
 CONFIG_OF_LIBFDT=y