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/ls1043ardb_sdcard_defconfig b/configs/ls1043ardb_sdcard_defconfig
index 65d3420..3224b86 100644
--- a/configs/ls1043ardb_sdcard_defconfig
+++ b/configs/ls1043ardb_sdcard_defconfig
@@ -1,5 +1,6 @@
 CONFIG_ARM=y
 CONFIG_TARGET_LS1043ARDB=y
+CONFIG_SPL_I2C_SUPPORT=y
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_DRIVERS_MISC_SUPPORT=y
 CONFIG_DEFAULT_DEVICE_TREE="fsl-ls1043a-rdb"