Regenerate config files

CONFIG_EXT4_FS is compiled on kernel for all machines
CONFIG_EXT3_FS is compiled as kernel module for all machines
CONFIG_MTD_NAND_NANDSIM is compiled as kernel module for all machines

With EXT4 compiled on kernel we can mount also ext3/ext2, so there is
no need to have EXT3 compiled on kernel.

Additionally enable NANDSIM as kernel module, required by OpenMultiboot.