armvirt: add 5.15 as testing kernel

Add 5.15 as testing kernel.

Signed-off-by: Aleksander Jan Bajkowski <[email protected]>

target/linux/armvirt/Makefile

@@ -10,6 +10,7 @@ FEATURES:=fpu pci rtc usb
 FEATURES+=cpiogz ext4 ramdisk squashfs targz
 
 KERNEL_PATCHVER:=5.10
+KERNEL_TESTING_PATCHVER:=5.15
 
 include $(INCLUDE_DIR)/target.mk