sunxi: 6.6: set testing kernel

Allow selecting 6.6 as testing kernel on sunxi.

Runtime-tested:
 - Linksprite pcDuino (cortexa8)
 - Olimex A20 Micro (cortexa7)
 - Pine64 SoM (cortexa53)

Signed-off-by: Zoltan HERPAI <[email protected]>

target/linux/sunxi/Makefile

@@ -11,6 +11,7 @@ FEATURES:=usb ext4 display rootfs-part rtc squashfs
 SUBTARGETS:=cortexa8 cortexa7 cortexa53
 
 KERNEL_PATCHVER:=6.1
+KERNEL_TESTING_PATCHVER:=6.6
 
 KERNELNAME:=zImage dtbs