[openwrt/openwrt] realtek: add Linux Kernel 5.15 as testing version

[LEDE Commits]

svanheule pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/88db7461cf2bea1e21bdaee2091908cd38e00bc3

commit 88db7461cf2bea1e21bdaee2091908cd38e00bc3
Author: INAGAKI Hiroshi <musashino.open at gmail.com>
AuthorDate: Tue Mar 29 14:50:13 2022 +0900

    realtek: add Linux Kernel 5.15 as testing version
    
    Add Linux Kernel 5.15 support for testing.
    
    Signed-off-by: INAGAKI Hiroshi <musashino.open at gmail.com>
    [APRESIA ApresiaLightGS120GT-SS, Panasonic Switch-M24eG PN28240K, Switch-M48eG PN28480K]
    Tested-by: INAGAKI Hiroshi <musashino.open at gmail.com>
    TP-Link TL-SG2008P
    Tested-by: Alexandru Gagniuc <mr.nuke.me at gmail.com>
    [D-Link DGS-1210-20, DGS-1210-52, Zyxel XGS1010-12]
    Tested-by: Markus Stockhausen <markus.stockhausen at gmx.de>
    [Zyxel XGS1250-12]
    Tested-by: Lucian Cristian <lucian.cristian at gmail.com> # Zyxel
    [HPE 1920-8G, 1920-48G]
    Tested-by: Jan Hoffmann <jan at 3e8.eu>
---
 target/linux/realtek/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/target/linux/realtek/Makefile b/target/linux/realtek/Makefile
index 037ba7ac7d..797ae60274 100644
--- a/target/linux/realtek/Makefile
+++ b/target/linux/realtek/Makefile
@@ -10,6 +10,7 @@ FEATURES:=ramdisk squashfs
 SUBTARGETS:=rtl838x rtl839x rtl930x rtl931x
 
 KERNEL_PATCHVER:=5.10
+KERNEL_TESTING_PATCHVER:=5.15
 
 define Target/Description
 	Build firmware images for Realtek RTL83xx based boards.