lpm_levels: Fix num_childs_in_sync initialization

Currently num_childs_in_sync does not get initialized as cluster
lookup returns NULL. Initialize the variable after per_cpu cluster
nodes are initialized.

Change-Id: Iae30debe7c52324d6e2cb666ef96ee894144358e
Signed-off-by: Archana Sathyakumar <asathyak@codeaurora.org>