busybox-mdev: use existing devtmpfs for /dev if mounted
busybox-mdev: use existing devtmpfs for /dev if mounted

If devtmpfs is already mounted on /dev use this instead of creating and
repopulating new tmpfs.

oe-lite/base,oe-lite/base,oe-lite/base,oe-lite/base,oe-lite/base,oe-lite/base