Add kernel 5.15 for RPI4 support

root/target/linux/bcm27xx/patches-5.15/0480-SQUASH-fbmem-Use-fallthrough-keyword.patch

@@ -0,0 +1,29 @@
+From d2f01c176f70c7047340748ecab0ba3a92ab8060 Mon Sep 17 00:00:00 2001
+From: Phil Elwell <phil@raspberrypi.com>
+Date: Tue, 27 Jul 2021 09:24:20 +0100
+Subject: [PATCH 480/634] SQUASH: fbmem: Use fallthrough keyword
+
+Avoid a compiler warning by using the "fallthrough" pseudo-keyword in
+place of the old "/* fall through */" comment convention.
+
+Signed-off-by: Phil Elwell <phil@raspberrypi.com>
+---
+ drivers/video/fbdev/core/fbmem.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
+index f9b620f6a074..13f3eca3049a 100644
+--- a/drivers/video/fbdev/core/fbmem.c
++++ b/drivers/video/fbdev/core/fbmem.c
+@@ -1201,7 +1201,7 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
+ 			ret = fb_copyarea_user(info, &copy);
+ 			break;
+ 		}
+-		/* fall through */
++		fallthrough;
+ 	default:
+ 		lock_fb_info(info);
+ 		fb = info->fbops;
+-- 
+2.33.1
+