ppc: Convert vas ID allocation to new IDA API

Removes a custom spinlock and simplifies the code.  Also fix an
error where we could allocate one ID too many.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

arch/powerpc/platforms/powernv/vas-window.c

@@ -515,35 +515,17 @@ int init_winctx_regs(struct vas_window *window, struct vas_winctx *winctx)
 	return 0;
 }
 
-static DEFINE_SPINLOCK(vas_ida_lock);
-
 static void vas_release_window_id(struct ida *ida, int winid)
 {
-	spin_lock(&vas_ida_lock);
-	ida_remove(ida, winid);
-	spin_unlock(&vas_ida_lock);
+	ida_free(ida, winid);
 }
 
 static int vas_assign_window_id(struct ida *ida)
 {
-	int rc, winid;
-
-	do {
-		rc = ida_pre_get(ida, GFP_KERNEL);
-		if (!rc)
-			return -EAGAIN;
-
-		spin_lock(&vas_ida_lock);
-		rc = ida_get_new(ida, &winid);
-		spin_unlock(&vas_ida_lock);
-	} while (rc == -EAGAIN);
-
-	if (rc)
-		return rc;
+	int winid = ida_alloc_max(ida, VAS_WINDOWS_PER_CHIP - 1, GFP_KERNEL);
 
-	if (winid > VAS_WINDOWS_PER_CHIP) {
-		pr_err("Too many (%d) open windows\n", winid);
-		vas_release_window_id(ida, winid);
+	if (winid == -ENOSPC) {
+		pr_err("Too many (%d) open windows\n", VAS_WINDOWS_PER_CHIP);
 		return -EAGAIN;
 	}