mm/early_ioremap.c: improve the execution efficiency of early_ioremap_setup()

Reduce the number of invalid loops of the function early_ioremap_setup()
to improve the efficiency of function execution

Link: https://lkml.kernel.org/r/CACZJ9cU6t5sLoDwE6_XOg+UJLpZt4+qHfjYN2bA0s+3y9y6pQQ@mail.gmail.comSigned-off-by: LiamNi <zhiguangni01@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/early_ioremap.c

@@ -72,12 +72,10 @@ void __init early_ioremap_setup(void)
 {
 	int i;
 
-	for (i = 0; i < FIX_BTMAPS_SLOTS; i++)
-		if (WARN_ON(prev_map[i]))
-			break;
-
-	for (i = 0; i < FIX_BTMAPS_SLOTS; i++)
+	for (i = 0; i < FIX_BTMAPS_SLOTS; i++) {
+		WARN_ON_ONCE(prev_map[i]);
 		slot_virt[i] = __fix_to_virt(FIX_BTMAP_BEGIN - NR_FIX_BTMAPS*i);
+	}
 }
 
 static int __init check_early_ioremap_leak(void)