qcacmn: Use atomic variant of qdf_mem_malloc for vdev stats

When kernel calls driver callback to get stats, dev_get_stats()->
ndo_get_stats64() .Host driver allocates memory using
kmalloc (size, GFP_KERNEL) routine,
but as ndo_get_stats is under RCU lock but not in interrupt
context(in_irq = 0, in_interrupt = 0, irq_disable = 1),
qdf_mem_malloc () uses ‘GFP_KERNEL’ to allocate memory,
leading to backtrace for sleeping function call from invalid
context.

As per kernel doc
(https://www.kernel.org/doc/Documentation/networking/statistics.rst),
while in ndo_get_stats64 () API, driver should not calling a routing
which can sleep. Use atomic variant of qdf_mem_malloc() to fix this.

Change-Id: I775f53dd1e8165e962321215e65d46142fb3b3cc
CRs-Fixed: 3128647

dp/wifi3.0/dp_main.c

@@ -8623,7 +8623,7 @@ static QDF_STATUS dp_vdev_getstats(struct cdp_vdev *vdev_handle,
 
 	soc = pdev->soc;
 
-	vdev_stats = qdf_mem_malloc(sizeof(struct cdp_vdev_stats));
+	vdev_stats = qdf_mem_malloc_atomic(sizeof(struct cdp_vdev_stats));
 
 	if (!vdev_stats) {
 		dp_cdp_err("%pK: DP alloc failure - unable to get alloc vdev stats",