vmx: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

The use of "rcu_assign_pointer()" is NULLing out the pointer. According to RCU_INIT_POINTER()'s block comment:
"1. This use of RCU_INIT_POINTER() is NULLing out the pointer"
it is better to use it instead of rcu_assign_pointer() because it has a smaller overhead.

The following Coccinelle semantic patch was used:
@@
@@

- rcu_assign_pointer
+ RCU_INIT_POINTER
(..., NULL)

---
 arch/x86/kvm/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 801332e..12b840c 100644
@@ -9029,7 +9029,7 @@ static void __exit vmx_exit(void)
 	free_page((unsigned long)vmx_vmread_bitmap);
 
 #ifdef CONFIG_KEXEC
-	rcu_assign_pointer(crash_vmclear_loaded_vmcss, NULL);
+	RCU_INIT_POINTER(crash_vmclear_loaded_vmcss, NULL);
 	synchronize_rcu();
 #endif
 

1.9.1