xfrm_policy: use true and false for boolean values

Assign true or false to boolean variables instead of an integer value.

This issue was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_policy.c

@@ -1740,7 +1740,7 @@ static void xfrm_pcpu_work_fn(struct work_struct *work)
 void xfrm_policy_cache_flush(void)
 {
 	struct xfrm_dst *old;
-	bool found = 0;
+	bool found = false;
 	int cpu;
 
 	might_sleep();