classes/image_live: allow different filesystems to be used for live images
The idea is copied from commit
df0b217f3df2c36a32e5c4afaec36a28bfc77bbb:
[ classes/image_vm: allow different filesystems to be used for VM images ]
The same logic should apply to image_live.bbclass, to allow other
filesystems to be used vs just ext4. The default value of ext4 is kept
so there is no functional change unless LIVE_ROOTFS_TYPE is set in the
inherting recipe.
Signed-off-by: Ming Liu <peter.x.liu@external.atlascopco.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
