kernel: don't remove of_tables

These are needed for OF setup of clocksource, clocks and irqchips.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@36657 3c298f89-4303-0410-b956-a3cf2f4a3e73