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>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37915 3c298f89-4303-0410-b956-a3cf2f4a3e73