qcacmn: Fix memleak issue in DFS component
Problem:
During wifi up/down, dfs_init_precac_list() is called to initialize
the precac list without de-allocating the previously allocated memory.
This leads to a memory leak.
Solution:
Deinit the allocated memory before initializing the precac list.
Change-Id: I7eee38fbc3c50f37ac0c6670b5bfe4b5a1b2d9f6
CRs-Fixed: 2140042