bcm4908: switch to kernel 5.10

Tested on:
1. Asus GT-AC5300
2. Netgear R8000P

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

target/linux/bcm4908/Makefile

@@ -9,8 +9,7 @@ FEATURES:=squashfs nand usb pci pcie gpio
 CPU_TYPE:=cortex-a53
 SUBTARGETS:=generic
 
-KERNEL_PATCHVER:=5.4
-KERNEL_TESTING_PATCHVER:=5.10
+KERNEL_PATCHVER:=5.10
 
 define Target/Description
 	Build firmware images for Broadcom BCM4908 SoC family routers.