x86: Update kernel for alix2 to 3.10.15

Without this patch, the patch
target/linux/generic/patches-3.10/770-bgmac-backport.patch
would not apply.

Signed-off-by: Tobias Steinicke <tsteinicke@net.t-labs.tu-berlin.de>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38438 3c298f89-4303-0410-b956-a3cf2f4a3e73