fixup! Wait for endptmngr during chan_brcm module load

Move creating of ubus thread after getting the endpt_id and
do not call ubus_lookup_id() afterwards since it can cause deadlock.
Ubus thread uses the same ctx (ubus context *) as the chan_brcm thread
while UBUS is not thread safe and ctx needs to be used by only one
thread in the same time.

Signed-off-by: Grzegorz Sluja <grzegorz.sluja@iopsys.eu>