Convert CONFIG_SPL_I2C_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/omap4_panda_defconfig b/configs/omap4_panda_defconfig
index b69124e..3dd7344 100644
--- a/configs/omap4_panda_defconfig
+++ b/configs/omap4_panda_defconfig
@@ -1,8 +1,9 @@
 CONFIG_ARM=y
 CONFIG_OMAP44XX=y
+# CONFIG_SPL_I2C_SUPPORT is not set
 CONFIG_TARGET_OMAP4_PANDA=y
-CONFIG_SPL=y
 CONFIG_VERSION_VARIABLE=y
+CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set