qcacmn: Remove qdf_flex_mem_release()

Due to a limitation in the memory leak detection logic when qdf_flex_mem
was written, qdf_flex_mem_release() was necessary to free any
dynamically allocated memory in the qdf_flex_mem_pool during certain
points in the WLAN driver lifecycle. This was done to avoid flagging any
dynamically allocated qdf_flex_mem_segments as false positive leaks
when the memory domains were changed and leak checking was performed.
With the introduction of qdf_talloc(), this workaround is no longer
required. Replace the calls to qdf_mem_malloc/free with qdf_talloc/free,
and remove qdf_flex_mem_release() altogether.

Change-Id: Ia5fd21386b94fc117af5f27853db5d8341601738
CRs-Fixed: 2404955
4 files changed