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/xpedite517x_defconfig b/configs/xpedite517x_defconfig
index 7b1f2b5..f7f8fd9 100644
--- a/configs/xpedite517x_defconfig
+++ b/configs/xpedite517x_defconfig
@@ -19,6 +19,7 @@
 CONFIG_CMD_DATE=y
 CONFIG_CMD_JFFS2=y
 CONFIG_CMD_IRQ=y
+CONFIG_CMD_PCA953X=y
 CONFIG_DS4510=y
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y