qcacmn: Use qdf_flex_mem for scheduler messages

Currently, the scheduler thread keeps a large, pre-allocated array of
messages for use in message posting. The vast majority of the time,
however, the scheduler thread has zero or one messages pending in the
queue. This leads to a huge memory overhead for nominal driver
operation.

Replace the current pre-allocated scheduler message pool with a
hybrid static/dynamic approach.

Change-Id: Ie942bacfef43edf142a9f35ad0309069096cda90
CRs-Fixed: 2204172

qdf/src/qdf_flex_mem.c

@@ -195,3 +195,4 @@ void qdf_flex_mem_release(struct qdf_flex_mem_pool *pool)
 	qdf_spin_unlock_bh(&pool->lock);
 }
 qdf_export_symbol(qdf_flex_mem_release);
+