Convert CONFIG_SPL_LIBCOMMON_SUPPORT to Kconfig

Move this option to Kconfig and tidy up existing uses.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/mx28evk_defconfig b/configs/mx28evk_defconfig
index af8bd82..1f0610f 100644
--- a/configs/mx28evk_defconfig
+++ b/configs/mx28evk_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_TARGET_MX28EVK=y
 CONFIG_SPL_GPIO_SUPPORT=y
+CONFIG_SPL_LIBCOMMON_SUPPORT=y
 CONFIG_FIT=y
 CONFIG_SYS_EXTRA_OPTIONS="ENV_IS_IN_MMC"
 CONFIG_BOOTDELAY=1