ar71xx: use the lzma loader for the WRT160NL

Partition layout before:
  0x000000040000-0x0000001a0000 : "kernel"
  0x0000001a0000-0x0000007e0000 : "rootfs"
  mtd: partition "rootfs" set to be root filesystem
  mtd: partition "rootfs_data" created automatically, ofs=0x350000, len=0x490000
  0x000000350000-0x0000007e0000 : "rootfs_data"

after:
  0x000000040000-0x000000140000 : "kernel"
  0x000000140000-0x0000007e0000 : "rootfs"
  mtd: partition "rootfs" set to be root filesystem
  mtd: partition "rootfs_data" created automatically, ofs=0x2f0000, len=0x4f0000
  0x0000002f0000-0x0000007e0000 : "rootfs_data"

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 37915