Convert CONFIG_EMIF4 et al to Kconfig

This converts the following to Kconfig:
   CONFIG_EMIF4
   CONFIG_SDRC

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefano Babic <sbabic@denx.de>
diff --git a/configs/cm_t3517_defconfig b/configs/cm_t3517_defconfig
index ba7d813..4df40d6 100644
--- a/configs/cm_t3517_defconfig
+++ b/configs/cm_t3517_defconfig
@@ -3,6 +3,7 @@
 CONFIG_ARCH_OMAP2PLUS=y
 CONFIG_SYS_TEXT_BASE=0x80008000
 CONFIG_TARGET_CM_T3517=y
+CONFIG_EMIF4=y
 CONFIG_BOOTDELAY=3
 # CONFIG_CONSOLE_MUX is not set
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y