mx25pdk: Use generic filesystem commands

This rework the board to use the generic filesystem commands instead
of forcing the use of FAT for the boot files.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
diff --git a/configs/mx25pdk_defconfig b/configs/mx25pdk_defconfig
index 1fd33dc..1ea58ee 100644
--- a/configs/mx25pdk_defconfig
+++ b/configs/mx25pdk_defconfig
@@ -14,7 +14,8 @@
 CONFIG_CMD_PING=y
 CONFIG_CMD_CACHE=y
 CONFIG_CMD_DATE=y
-CONFIG_CMD_EXT2=y
-CONFIG_CMD_FAT=y
+CONFIG_CMD_FS_GENERIC=y
+CONFIG_DOS_PARTITION=y
 CONFIG_ENV_IS_IN_MMC=y
+CONFIG_FS_FAT=y
 CONFIG_OF_LIBFDT=y