Convert CONFIG_CMD_PCA953X to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_PCA953X

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/configs/ot1200_spl_defconfig b/configs/ot1200_spl_defconfig
index 34331ca..712dcde 100644
--- a/configs/ot1200_spl_defconfig
+++ b/configs/ot1200_spl_defconfig
@@ -33,6 +33,7 @@
 CONFIG_CMD_FAT=y
 CONFIG_CMD_FS_GENERIC=y
 CONFIG_DM=y
+CONFIG_CMD_PCA953X=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_MACRONIX=y
 CONFIG_SPI_FLASH_STMICRO=y