This allows the selection of a specific branch in the menuconfig
when using a kernel downloaded from GIT.

Signed-off-by: Mathieu Olivari <mathieu@qca.qualcomm.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@40946 3c298f89-4303-0410-b956-a3cf2f4a3e73