cnss_prealloc: fix GFP flag for mempool_alloc

As per implementation of might_sleep(), rcu_read_lock()
nesting depth should be take into consideration too to
figure out whether sleeping is allowable or not.
To make align with it, allocate memory with GFP_ATOMIC
if rcu_read_lock() nesting depth is not zero.

Change-Id: Ib225a33b1a3f37b919e41daf064ce2de44428973
CRs-Fixed: 3271651

cnss_prealloc/cnss_prealloc.c

@@ -195,7 +195,8 @@ void *wcnss_prealloc_get(size_t size)
 	gfp_t gfp_mask = __GFP_ZERO;
 	int i;
 
-	if (in_interrupt() || irqs_disabled())
+	if (in_interrupt() || irqs_disabled() ||
+	    in_atomic() || rcu_preempt_depth())
 		gfp_mask |= GFP_ATOMIC;
 	else
 		gfp_mask |= GFP_KERNEL;