coding guidelines: comply with MISRA Rule 12.1.

added parentheses verifying lack of ambiguities

Signed-off-by: Hess Nathan <nhess@baumer.com>
diff --git a/kernel/kheap.c b/kernel/kheap.c
index fd29df2..ccdd669 100644
--- a/kernel/kheap.c
+++ b/kernel/kheap.c
@@ -123,7 +123,7 @@
 	sys_heap_free(&heap->heap, mem);
 
 	SYS_PORT_TRACING_OBJ_FUNC(k_heap, free, heap);
-	if (IS_ENABLED(CONFIG_MULTITHREADING) && z_unpend_all(&heap->wait_q) != 0) {
+	if (IS_ENABLED(CONFIG_MULTITHREADING) && (z_unpend_all(&heap->wait_q) != 0)) {
 		z_reschedule(&heap->lock, key);
 	} else {
 		k_spin_unlock(&heap->lock, key);