kernel: disable the bluetooth in .config

bluetooth is not a general feature of the R1D.
There is no bluetooth device in the Router.

Disable it to speedup the kernel boot time.

Signed-off-by: Jack Tan <jiankemeng@gmail.com>
kernel: fixup the init script in the ramfs

Disable the upnet() to make the ethnet working when system up

Return the process to /lib/preinit.sh after the real rootfs
mounted

Signed-off-by: Jack Tan <jiankemeng@gmail.com>