brcm63xx: switch to 3.9 kernel

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@36947 3c298f89-4303-0410-b956-a3cf2f4a3e73
brcm63xx: remove support for 3.8 kernel

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@36948 3c298f89-4303-0410-b956-a3cf2f4a3e73
brcm63xx: simplify HCS image creation

$(KDIR)/vmlinux is already a binary image, there is no need to create
another one.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@36949 3c298f89-4303-0410-b956-a3cf2f4a3e73