Convert CONFIG_CMD_JFFS2 to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_JFFS2

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/TQM823L_LCD_defconfig b/configs/TQM823L_LCD_defconfig
index 61601a5..ccb68b2 100644
--- a/configs/TQM823L_LCD_defconfig
+++ b/configs/TQM823L_LCD_defconfig
@@ -14,6 +14,7 @@
 CONFIG_CMD_BMP=y
 CONFIG_CMD_DATE=y
 CONFIG_CMD_EXT2=y
+CONFIG_CMD_JFFS2=y
 CONFIG_MAC_PARTITION=y
 CONFIG_DOS_PARTITION=y
 # CONFIG_MMC is not set