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/orangepi_plus2e_defconfig b/configs/orangepi_plus2e_defconfig
index 2374f1d..c42f15b 100644
--- a/configs/orangepi_plus2e_defconfig
+++ b/configs/orangepi_plus2e_defconfig
@@ -8,6 +8,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="sun8i-h3-orangepi-plus2e"
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
 CONFIG_SPL=y
+CONFIG_SPL_I2C_SUPPORT=y
 CONFIG_SYS_EXTRA_OPTIONS="MACPWR=SUNXI_GPD(6)"
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set