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/edb9315a_defconfig b/configs/edb9315a_defconfig
index e7b4810..bb67881 100644
--- a/configs/edb9315a_defconfig
+++ b/configs/edb9315a_defconfig
@@ -15,6 +15,7 @@
 CONFIG_CMD_EXT2=y
 CONFIG_CMD_EXT4=y
 CONFIG_CMD_FAT=y
+CONFIG_CMD_JFFS2=y
 # CONFIG_DOS_PARTITION is not set
 CONFIG_LED_STATUS=y
 CONFIG_LED_STATUS0=y