brcm47xx: use kernel 4.9 by default

Kernel 4.9 is now working on the brcm47xx boards, we just recently fixed
the problem that some boards did not boot at all, by changing the memory
regions used to relocate the kernel to in the loader.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/brcm47xx/Makefile

@@ -13,7 +13,7 @@ FEATURES:=squashfs usb
 SUBTARGETS:=generic mips74k legacy
 MAINTAINER:=Hauke Mehrtens <hauke@hauke-m.de>
 
-KERNEL_PATCHVER:=4.4
+KERNEL_PATCHVER:=4.9
 
 define Target/Description
 	Build firmware images for Broadcom based BCM47xx/53xx routers with MIPS CPU, *not* ARM.