bcm4908: set kernel 6.6 as a testing version

Add kernel 6.6 for testing.

Signed-off-by: Mieczyslaw Nalewaj <[email protected]>

target/linux/bcm4908/Makefile

@@ -10,6 +10,7 @@ CPU_TYPE:=cortex-a53
 SUBTARGETS:=generic
 
 KERNEL_PATCHVER:=6.1
+KERNEL_TESTING_PATCHVER:=6.6
 
 define Target/Description
 	Build firmware images for Broadcom BCM4908 SoC family routers.